Apparatus for backside wafer processing with edge-only wafer contact - Patents.com

Abstract

Disclosed is a semiconductor processing tool having wafer backside processing capability. Such tools may be configured to contact the wafer being processed only through edge contact, as opposed to underside / flat contact. Such tools may also include wafer centering features that may enable such wafers to be precisely centered with respect to their particular wafer processing station.

Description

[Technical field]

[0001] Related Applications A PCT application is being filed contemporaneously herewith as a part of this application. Each application to which this application claims benefit or priority, as identified in the contemporaneously filed PCT application, is hereby incorporated by reference in its entirety for all purposes. [Background technology]

[0002] Semiconductor processing tools typically include one or more pedestals that are used to support semiconductor wafers within a semiconductor processing chamber. Such pedestals feature a wafer support surface on which wafers are placed and that is designed to support those wafers during semiconductor processing operations within the semiconductor processing chamber. The pedestal may include any of a variety of auxiliary systems including, for example, a vacuum chuck and / or an electrostatic chuck (which may provide the wafer support surface of the pedestal), a heating and / or cooling system, an electrode used for radio frequency energy transfer purposes, a purge gas system to protect the underside of the wafer from process gases that are intended to be applied only to the upwardly facing side of the wafer, a lift pin mechanism that may be used to raise the wafer off of (or lower the wafer onto) the wafer support surface, and the like. In such tools, the top surface of the wafer undergoes wafer processing operations while the bottom surface of the wafer rests on the pedestal. The wafer is typically secured in place on the pedestal using vacuum or electrostatic forces to maximize thermal coupling between the wafer and the pedestal, maintain flatness of the wafer during processing, and / or reduce the likelihood of process gases reaching the underside of the wafer. In some such semiconductor processing tools, a showerhead (sometimes called a gas distributor) may be positioned above the pedestal. The showerhead may have multiple gas distribution ports distributed across its surface facing the pedestal. Such gas distribution ports are fluidly connected to one or more plenums disposed within the showerhead. The one or more plenums are fluidly connected to one or more process gas sources, which may be controlled to selectively flow process gases across the top surface of the wafer supported by the pedestal.

[0003] A relatively new type of semiconductor processing tool, described in U.S. Patents Nos. 9,881,788 and 10,851,457, operates in a fundamentally different manner from the semiconductor processing tools described above. In such newer semiconductor processing tools, the pedestal on which the wafer normally rests during semiconductor processing operations is replaced with a shower pedestal, which is a pedestal-like structure having multiple gas distribution ports distributed across its upper surface (much like a showerhead having multiple gas distribution ports distributed across its lower surface). The gas distribution ports are fluidly connected to one or more plenums disposed within the shower pedestal. The one or more plenums are fluidly connected to one or more process gas sources, which are controllable to allow process gas to flow out of the shower pedestal through the gas distribution ports. Such semiconductor processing tools may also have one or more carrier ring supports, which may be configured to support a carrier ring, which may support the wafer during processing operations. The carrier ring support or supports are designed to allow the carrier ring, and any wafer supported by the carrier ring, to be held at an elevated position above the shower pedestal, such that there is a gap between the shower pedestal and the wafer through which process gases can be delivered. Such semiconductor processing tools thus allow the underside of the wafer to undergo wafer processing operations instead of the topside, a complete reversal from conventional wafer processing approaches. Summary of the Invention

[0004] The details of one or more embodiments of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims.

[0005] In some embodiments, an apparatus may be provided that includes a shower pedestal having a plurality of first gas distribution ports distributed across a first surface thereof. The first surface of the shower pedestal may define a first average midplane. The apparatus may further include a plurality of wafer support structures extending from the shower pedestal and positioned about a first reference axis, the first reference axis intersecting the first surface of the shower pedestal and being perpendicular to the first average midplane. The plurality of wafer support structures may be further positioned around an area including the first surface of the shower pedestal, each wafer support structure may have a corresponding wafer support surface that is non-parallel to the first average midplane, and each wafer support surface may have a portion positioned at least a first distance away from the first average midplane in a direction perpendicular to the first average midplane and a second distance away from the first reference axis in a direction perpendicular to the first reference axis.

[0006] In some further embodiments, at least a portion of each wafer support surface may form an angle greater than zero degrees and less than or equal to 15 degrees with respect to the first mean midplane.

[0007] In some further implementations, each wafer support structure may include a corresponding cantilever structure and a corresponding riser structure, For each wafer support structure, the corresponding cantilever structure for that wafer support structure may extend radially inward from the corresponding riser structure for that wafer support structure toward the first reference axis, the corresponding cantilever structure for that wafer support structure may have a proximal end connected to the corresponding riser structure for that wafer support structure, and the corresponding cantilever structure for that wafer support structure may have a distal end at which the corresponding wafer support surface for that wafer support structure is disposed.

[0008] In some further embodiments, each cantilever structure may have a corresponding channel on a side of the cantilever structure facing away from the first mean midplane, the corresponding channel of each cantilever structure may be disposed between the wafer support surface of the cantilever structure and a corresponding riser structure connected to a proximal end of the cantilever structure, and the corresponding channel of each cantilever structure may extend across the cantilever structure in a direction transverse to the long axis of the cantilever structure.

[0009] In some further embodiments, each channel may be at least 0.75 mm deep.

[0010] In some further embodiments, the apparatus can further include a plurality of wafer centering features, each having a corresponding centering surface, at least a portion of the centering surface of each wafer centering feature can be positioned a third distance from the first reference axis and can face the first reference axis.

[0011] In some further embodiments, the third distance may be between 150.5 mm and 150 mm.

[0012] In some further embodiments, each wafer centering feature may be fixed to and supported by a corresponding one of the wafer support structures via a gap.

[0013] In some further embodiments, at least a portion of the centering surface of each wafer centering feature may form an angle of less than 90 degrees with respect to the first reference axis.

[0014] In some further embodiments, at least a portion of the centering surface of each wafer centering feature may form an acute angle with the first reference axis that is greater than 0 degrees and less than or equal to 30 degrees.

[0015] In some further embodiments, the wafer centering features may be wheels. In some further embodiments, the wheels may be made of a ceramic material. In some further embodiments, each wheel may be supported by a corresponding one of the wafer support structures relative to the shower pedestal and may be configured to rotate about an axis that is a fixed distance relative to the first mean midplane.

[0016] In some further embodiments, the apparatus further includes a showerhead having a plurality of second gas distribution ports distributed across a second surface of the showerhead facing the first surface of the shower pedestal. In such embodiments, there may be N wheels, and the second surface of the showerhead may have N recesses therein, each recess may be positioned such that a corresponding second reference axis passes through the recess, the second reference axis being perpendicular to the first mean mid-plane and passing through the center of a corresponding one of the wheels.

[0017] In some further implementations, the apparatus may further include a focus ring. The focus ring may have a nominally circular inner edge with a diameter less than twice the third distance and a nominally circular outer edge with a diameter greater than twice the third distance. The focus ring may also be configured to rest on the wafer support structure and may include N openings proximate the inner edge or N notches along the inner edge, each positioned such that a portion of a corresponding one of the wheels passes through the opening or notch when the focus ring is supported by the wafer support structure.

[0018] In some implementations, the focus ring can have a top surface and a bottom surface and can be associated with a central axis and a reference surface that is normal to the central axis and coincident with the top surface. In such implementations, the bottom surface can have a first circumferential contour at a radial distance X from the central axis, the first circumferential contour varying such that a perpendicular distance from the reference surface to the bottom surface at the radial distance X varies periodically between at least a first value and a second value. In such implementations, twice the value of X can be greater than the diameter of the nominally circular inner edge and less than the diameter of the nominally circular outer edge.

[0019] In some implementations, the focus ring can further include a plurality of protrusions positioned along the bottom surface, each protrusion having a portion located a radial distance X from the central axis.

[0020] In some implementations, each protrusion can extend along a corresponding axis that is coplanar with a corresponding reference surface, the corresponding reference surface being coplanar with the central axis.

[0021] In some embodiments, each protrusion may be semi-cylindrical in shape.

[0022] In some implementations, the focus ring may have an inner portion and an outer portion, the inner edge may be disposed on the inner portion, the inner portion may be dimensioned such that it cannot pass through an opening defined by an innermost edge of the outer portion, and the inner portion and outer portion may not be fixedly connected to one another.

[0023] In some further implementations, the apparatus may include one or more wheel vertical lifting mechanisms, each wheel may be supported by a corresponding wheel riser structure, the one or more vertical lifting mechanisms may be configured to generally support the wheel riser structure and be movable between at least a first configuration and a second configuration, at least a portion of each wheel may be located farther from the first mean mid-plane than the wafer support surface in a direction parallel to the first reference axis when the one or more vertical lifting mechanisms are in the first configuration, and each wheel may be located between the first mean mid-plane and a location where the wheel was when the one or more vertical lifting mechanisms were in the first configuration when the one or more vertical lifting mechanisms are in the second configuration.

[0024] In some further implementations, the one or more vertical lifting mechanisms may be further configured to be movable between at least a first configuration, a second configuration, and further a third configuration, and the first mean midplane may be located between the wafer support surface and at least a portion of each wheel when the one or more vertical lifting mechanisms are in the third configuration.

[0025] In some further embodiments, each wheel riser structure may pass through a corresponding notch in the outer edge of the shower pedestal or through a corresponding hole through the shower pedestal.

[0026] In some further implementations, each wheel riser structure may be disposed at a different angular position about the first reference axis than the wafer support structure.

[0027] In some further implementations, each wheel riser structure may be disposed at the same angular position about the first reference axis as a corresponding one of the wafer support structures.

[0028] In some further implementations, each wafer support structure can have an opening therethrough that is dimensioned such that a portion of a corresponding one of the wheel riser structures passes through the opening when the one or more vertical lifting mechanisms are moved between the first configuration and the second configuration.

[0029] In some further implementations, the apparatus may further include the chamber and a rotary indexer having a plurality of forks. The rotary indexer may be configured to rotate the plurality of forks about a first axis of rotation to at least a first rotational position in response to one or more inputs, each fork may have a plurality of wafer lifting surfaces, and a first fork of the plurality of forks may be positioned such that a wafer lifting surface of the first fork is positioned above the shower pedestal when the plurality of forks is in the first rotational position.

[0030] In some further embodiments, the first fork can include two arms that are located completely outside of a circular area centered on the first reference axis and having a diameter twice the third distance when the multiple forks are in the first rotational position, and each of the arms can have one or more protrusions that extend inwardly toward the first reference axis such that a portion of each protrusion having one of the wafer lifting surfaces is located within the circular area when the multiple forks are in the first rotational position.

[0031] In some further embodiments, each wafer lifting surface may be non-parallel to the first mean midplane.

[0032] In some further embodiments, at least a portion of each wafer lifting surface may form an angle greater than zero degrees and less than or equal to 25 degrees with respect to the first mean midplane.

[0033] In some further implementations, the forks may each include a first half and a second half, at least one of the wafer lifting surfaces of each fork may be provided by the first half of that fork and at least one other of the wafer lifting surfaces of each fork may be provided by the second half of that fork, the first half of the fork may be fixed via a gap to a first hub and the second half of the fork may be fixed via a gap to a second hub, the first hub may be connected to a first rotational drive by a first shaft and the second hub may be connected to a second rotational drive by a second shaft, and the first rotational drive and the second rotational drive may be configured to be independently actuated for at least a portion of their rotational range of motion.

[0034] In some embodiments, an apparatus may be provided for use with a semiconductor wafer of diameter D. Such an apparatus may include a ring structure having an inner periphery defining an opening sized smaller than the semiconductor wafer of diameter D and an outer periphery sized larger than the semiconductor wafer of diameter D. The ring structure may have a top surface and a bottom surface and may be associated with a central axis and a reference plane perpendicular to the central axis and coincident with the top surface. The bottom surface may have a first circumferential contour at a radial distance X from the central axis, the first circumferential contour varying such that a perpendicular distance from the reference plane to the bottom surface at the radial distance X varies between at least a first value and a second value. X may be less than 50% of D.

[0035] In some embodiments, the vertical distance from the reference plane to the bottom surface at the radial distance X may vary periodically.

[0036] In some such embodiments, the vertical distance from the reference plane to the bottom surface at a radial distance X may vary periodically around the circumference of the ring structure with a periodicity of at least 3 periods.

[0037] In some embodiments, the vertical distance from the reference plane to the bottom surface at the radial distance X may vary periodically around the ring structure with a periodicity of three.

[0038] In some embodiments, the vertical distance from the reference plane to the bottom surface at the radial distance X may vary periodically around the ring structure with a periodicity of four.

[0039] In some such embodiments, the perpendicular distance from the reference plane to the bottom surface at a radial distance X may vary periodically around the circumference of the ring structure with a periodicity of at least 4 periods and no more than 10 periods.

[0040] In some such embodiments, the vertical distance from the reference plane to the bottom surface at a radial distance X may vary periodically around the ring structure with a periodicity of more than 10 periods and less than or equal to 20 periods.

[0041] In some such embodiments, the vertical distance from the reference plane to the bottom surface at a radial distance X may vary periodically around the ring structure with a periodicity of more than 20 periods and less than or equal to 30 periods.

[0042] In some implementations, there may be N spaced apart first locations around the ring structure, where a perpendicular distance from the reference plane to the bottom surface at a radial distance X is at a first value, and there may be N spaced apart second locations around the ring structure, where a perpendicular distance from the reference plane to the bottom surface at a radial distance X is at a second value, and each first location may be circumferentially interspaced between two of the second locations, and each second location may be circumferentially interspaced between two of the first locations, where N may be an integer greater than or equal to 3.

[0043] In some such embodiments, N can be 3 or 4. In some other embodiments, N can be an integer greater than 3 and less than or equal to 30, an integer greater than 3 and less than or equal to 10, an integer greater than 10 and less than or equal to 20, or an integer greater than 20 and less than or equal to 30.

[0044] In some embodiments, the absolute value of the difference between the first value and the second value may be greater than zero microns and less than or equal to 400 microns.

[0045] In some embodiments, the absolute value of the difference between the first value and the second value can be greater than zero microns and less than or equal to 100 microns, greater than or equal to 50 microns and less than or equal to 150 microns, greater than or equal to 100 microns and less than or equal to 200 microns, greater than or equal to 150 microns and less than or equal to 250 microns, greater than or equal to 200 microns and less than or equal to 300 microns, greater than or equal to 250 microns and less than or equal to 350 microns, or greater than or equal to 300 microns and less than or equal to 400 microns.

[0046] In some embodiments, the absolute value of the difference between the first value and the second value may be greater than a maximum expected amount of wafer edge sag in a semiconductor wafer when the semiconductor wafer is supported at multiple locations along its edge by a third value. In some such embodiments, the third value may be greater than zero microns and less than or equal to 50 microns. In some other such embodiments, the third value may be greater than zero microns and less than or equal to 40 microns. In some other such embodiments, the third value may be greater than zero microns and less than or equal to 30 microns. In some other such embodiments, the third value may be greater than 20 microns and less than or equal to 20 microns.

[0047] In some embodiments, the top surface can be planar or at least axisymmetric about the central axis, hi some other embodiments, the top surface can have a second circumferential contour that follows the first circumferential contour.

[0048] In some embodiments, the bottom surface at a radial distance X from the central axis can be a wavy frustum of a cone.

[0049] In some embodiments, the bottom surface at a radial distance X from the central axis may have a radial profile relative to the central axis that is at an oblique angle to the central axis.

[0050] In some embodiments, the ring structure may be made of a ceramic material, hi some such embodiments, the ceramic material may be aluminum oxide.

[0051] In the discussion that follows, reference is made to the following figures, which are not intended as limiting in scope but are provided merely to facilitate the discussion that follows: [Brief description of the drawings]

[0052] [Figure 1] FIG. 1 illustrates an exemplary shower pedestal and associated structure.

[0053] [Diagram 2] FIG. 2 shows a shower pedestal similar to that shown in FIG. 1.

[0054] [Diagram 3] FIG. 2 is a detailed view of the portion of FIG. 1 enclosed within the dashed-dotted circle.

[0055] [Figure 4] FIG. 4 is an isometric detail view of an embodiment of the wafer centering feature and wafer support structure shown in FIGS. 1-3.

[0056] [Figure 4-] FIG. 5 is a view of the same embodiment as FIG. 4, with the wheels retracted into the shower pedestal.

[0057] [Diagram 5] FIG. 2 illustrates an exemplary embodiment in which a wafer centering feature is circumferentially offset relative to a first reference axis relative to the wafer support structure.

[0058] [Figure 5-] FIG. 6 is a view of the same embodiment as FIG. 5, with the wheel riser structure retracted into the shower pedestal.

[0059] [Figure 6] 1 is a diagram of an exemplary wafer centering feature supported by and fixed via a gap to the wafer support structure;

[0060] [Figure 7] 1 illustrates an exemplary embodiment of a wafer support structure having a wafer centering feature that includes a protrusion.

[0061] [Figure 8] FIG. 2 is a diagram of an example shower pedestal, as well as a showerhead and focus ring.

[0062] [Figure 9] FIG. 9 is a diagram of the showerhead and shower pedestal of FIG. 8 positioned as they would be during an actual wafer processing operation.

[0063] [Figure 10] FIG. 5 is a diagram of an example of a shower pedestal including a showerhead and a wafer support structure similar to those shown in FIGS. 4 and 4'.

[0064] [Figure 11] FIG. 1 is an isometric view of a shower pedestal including four wafer support structures.

[0065] [Figure 12] FIG. 1 is a diagram of an exemplary four station semiconductor processing tool.

[0066] [Figure 13] FIG. 2 is a perspective view of an exemplary fork including a wafer.

[0067] [Figure 14] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 15] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 16] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 17] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 17-] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 18] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 19] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 19-] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 20] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 21] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 22] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 23] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 24] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Diagram 25]FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation. [Figure 26] FIG. 13 is a diagram of a four station arrangement similar to that shown in FIG. 12 during one stage of a wafer placement and positioning operation.

[0068] [Figure 27] 1 is a simplified schematic diagram of a semiconductor processing tool having features and systems as discussed below.

[0069] [Figure 28] FIG. 1 is a diagram of a rotary indexer including openable and closable forks. [Figure 29] FIG. 1 is a diagram of a rotary indexer including openable and closable forks. [Diagram 30] FIG. 1 is a diagram of a rotary indexer including openable and closable forks. [Diagram 31] FIG. 1 is a diagram of a rotary indexer including openable and closable forks.

[0070] [Diagram 32] FIG. 1 illustrates an example of a wafer supported on a shower pedestal and exhibiting wafer edge bowing.

[0071] [Diagram 33] FIG. 33 is a side view of FIG. 32.

[0072] [Diagram 34] FIG. 2 is a top view of an exemplary ring structure, wafer, and shower pedestal.

[0073] [Diagram 35] FIG. 35 is a diagram of the exemplary ring structure and circumferential contour of the wafer of FIG. 34. [Diagram 36] FIG. 35 is a diagram of the exemplary ring structure and circumferential contour of the wafer of FIG. 34.

[0074] [Figure 37]FIG. 2 is a top view of the ring structure and the wafer.

[0075] [Figure 38] FIG. 37 is a cross-sectional view of FIG.

[0076] [Figure 39] FIG. 39 is a detailed view of FIG. 38.

[0077] [Diagram 40] FIG. 2 is a biaxial view of a ring structure including an axisymmetric top surface. [Diagram 41] FIG. 2 is a biaxial view of a ring structure including an axisymmetric top surface.

[0078] [Diagram 42] FIG. 1 is a biaxial view of a ring structure including a top surface having a varying circumferential contour. [Diagram 43] FIG. 1 is a biaxial view of a ring structure including a top surface having a varying circumferential contour.

[0079] [Diagram 44] FIG. 2 is a side view of an exemplary shower pedestal including an exemplary ring structure and a wafer. [Diagram 45] FIG. 2 is a side view of an exemplary shower pedestal including an exemplary ring structure and a wafer.

[0080] [Diagram 46] FIG. 13 is an isometric bottom view of an exemplary ring structure having six protrusions disposed on the bottom surface.

[0081] [Figure 47] FIG. 47 is a detailed view of a portion of the ring structure of FIG. 46.

[0082] [Figure 48] FIG. 2 is an isometric cross-sectional view of an exemplary showerhead and shower pedestal supporting a wafer.

[0083] [Figure 49] FIG. 49 is a detailed view of the circled portion of FIG. 48. [Figure 50] FIG. 49 is a detailed view of the circled portion of FIG. 48. [Figure 51] FIG. 49 is a detailed view of the circled portion of FIG. 48.

[0084] [Figure 52] FIG. 2 is an isometric view of a focus ring including an inner portion and an outer portion.

[0085] [Figure 53] FIG. 53 is an isometric view of the focus ring of FIG. 52 with the inner portion lifted away from the outer portion.

[0086] [Figure 54] FIG. 53 is a cross-sectional view of the focus ring of FIG. 52.

[0087] [Figure 55] This is a detailed view of the circled portion in Figure 54. In the original text, "'" is used to explain the figure, but in the translated text, "-" is used for convenience. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] The above figures are provided to facilitate understanding of the concepts discussed in the present disclosure and are intended to be illustrative of some embodiments falling within the scope of the present disclosure, but are not intended to be the limiting embodiments consistent with the present disclosure, and embodiments not shown in the figures are still deemed to be within the scope of the present disclosure.

[0089] Disclosed herein are systems and apparatus for use in semiconductor processing tools that perform processing operations on the underside of a substrate (also referred to herein simply as a "wafer"). As mentioned above, U.S. Patent Nos. 9,881,788 and 10,851,457 describe examples of semiconductor processing tools designed to facilitate performing wafer processing operations on the underside of a wafer. Such systems use a carrier ring to support such wafers during such operations, the carrier ring being supported above a shower pedestal that supports the wafer above the shower pedestal such that there is a gap, e.g., at least a few millimeters, between the underside of the wafer and the surface of the shower pedestal directly below it. However, the carrier ring in such systems contacts the underside of the wafer in a number of smaller areas, e.g., along an annular area extending radially inward from the edge of the wafer on a corresponding annular area of ​​the carrier ring, or on tabs extending radially inward from the inner periphery of the carrier ring. In either case, the surface on which the wafer rests may be in planar contact with the underside of the wafer. It has been determined that such wafer supports, in some cases, result in an undesirable "shadowing" effect, where areas of the wafer at or immediately adjacent the surface of the wafer in contact with the carrier ring do not receive the same amount of processing as the remainder of the wafer. For example, such areas may receive lower levels of deposition than other areas of the wafer. Such non-uniformities can reduce the effective area of ​​the wafer, thereby reducing wafer yield.

[0090] The inventors have come up with an apparatus, system, and method that allows such wafer backside processing to occur while supporting the wafer through edge contact, as opposed to through planar contact as is the case with the carrier ring-based systems described above. Supporting the wafer through edge contact can reduce or eliminate shadowing effects on the wafer, thereby reducing or eliminating the magnitude of non-uniformities that may occur on the underside of the wafer proximate the location where the wafer is supported. Additionally, such a system allows the wafer to be supported without the use of a carrier ring, thereby reducing cost, tool inventory, and complexity.

[0091] Wafers are typically provided with beveled or rounded top and bottom edges to reduce the likelihood of delamination, arcing, edge chipping, or other problems with the wafer during processing, however, the systems disclosed herein may be used with both beveled or rounded edge wafers or non-beveled or non-rounded edge wafers.

[0092] Various concepts related to the use of such edge-supported wafers during backside processing of the wafer are discussed below with respect to various figures.

[0093] FIG. 1 illustrates an exemplary shower pedestal and associated structure. As seen in the figure, the shower pedestal 104 contains a first plenum 110 and a number of first gas distribution ports 108 extending from a first surface 106 to the first plenum 110. The first gas distribution ports 108 may fluidly connect the first plenum 110 to a processing region positioned between the first surface 106 and the wafer 101, if present. A gas distribution port as a term used herein means a small port, orifice, hole, or opening in the shower pedestal or showerhead, depending on the context, through which gas can be supplied to the shower pedestal or showerhead via one or more gas inlets and then exit the shower pedestal or showerhead through the gas distribution port as needed. A large number of gas distribution ports, for example tens, hundreds, or in some cases thousands of gas distribution ports, may be distributed across a surface of the shower pedestal or showerhead facing the wafer during processing operations to deliver processing gases to the wafer in a desired manner. During semiconductor processing operations, the first plenum 110 may be provided with one or more process gases via a first gas inlet 112 that passes through a stem 105 that supports the shower pedestal 104 .

[0094] The shower pedestal 104 may generally include a sidewall extending around a first plenum 110, a bottom wall (which may extend from a stem 105 to the sidewall), and a top wall (through which a first gas distribution port 108 extends).

[0095] The mean midplane of a surface is a plane that intersects the surface and is positioned such that the maximum distance between the mean midplane and the point on that surface that is furthest from the mean midplane is minimized. For a first surface 106 that is a planar surface, such as the first surface 106 shown in FIG. 1, the first mean midplane 114 is a plane that is coplanar with the first surface 106.

[0096] FIG. 2 shows a shower pedestal 204 similar to the shower pedestal 104 shown in FIG. 1. Structures in FIG. 2 similar to corresponding structures in FIG. 1 are shown using callouts with the same last two digits, and the discussion of such elements with respect to FIG. 1 is equally applicable to the corresponding elements in FIG. 2. The only difference between the shower pedestal 104 and related components in FIG. 1 and the corresponding shower pedestal 204 and related components in FIG. 2 is that the shower pedestal 204 has a first surface 206 that is non-planar. In this example, the first surface 206 bulges toward the wafer 201 in the center, giving the first surface 206 a dome-shaped appearance. As can be seen, the first mean mid-plane 214 is no longer coplanar with the first surface 206 (which is not possible due to the curvature of the first surface 206). However, the volume captured between the first mean mid-plane 214 and the first surface 106 on either side of the first mean mid-plane 114 is equal, and the maximum distance between the first mean mid-plane 114 and the first surface 106 on either side of the first mean mid-plane 114 is minimal. Thus, the first mean mid-plane 114 can generally act as a stand-in for a planar first surface 106 in a shower pedestal 104 having a rounded first surface 106.

[0097] The first reference axis 116 generally represents the central axis of the shower pedestal, or, perhaps more precisely, may be positioned at a location intended to cause the first reference axis 116 to pass through the center of the wafer 101 when the wafer 101 is present and properly positioned.

[0098] The shower pedestal 104 can support multiple wafer support structures 138 that can be positioned at positions around the first surface 106; in this example, there are three wafer support structures 138, although other embodiments may have a different number of wafer support structures 138. Wafer support structure, as used herein, refers to a structure configured to have a wafer placed thereon and to support such wafer at an elevated position relative to the shower pedestal, i.e., such that there is a gap between the lower surface of the wafer and the top of the shower pedestal. The wafer support structure can be either a fixed structure, such as a static tower-like structure that protrudes from the top surface of the shower pedestal, a static tower-like structure that extends downward from a showerhead positioned above the shower pedestal, or a static cantilevered structure that extends radially inward from a wall of the semiconductor processing chamber, or a dynamic structure, such as a similar structure connected to an actuator that allows such structure to be moved between various positions, at least one of which correlates to a position where a wafer can be supported by such structure such that there is a gap between the lower surface of the wafer and the upper surface of the shower pedestal. Various examples of wafer support structures are discussed in more detail later in this disclosure.

[0099] FIG. 3 shows a detailed view of a portion of FIG. 1 enclosed within a dashed-dotted circle (which includes the wafer support structure 138 on the left). As seen in FIG. 3, the wafer support structures 138 may each have one or more corresponding wafer support surfaces 140. At least a portion of each wafer support surface 140 may be positioned a first distance 142 away from the first mean mid-plane 114 in a direction perpendicular to the first mean mid-plane and a second distance 144 away from the first reference axis 116 in a direction parallel to the first mean mid-plane 114. The first distance 142 may be, for example, on the order of a few millimeters to tens of millimeters, while the second distance 144 may be, for example, half the diameter of the innermost edge of the wafer 101 with which the shower pedestal is designed to be used. The wafer support surface 140 may be non-parallel to the first mean mid-plane 114 and may be at an acute non-zero angle α with the first mean mid-plane, such as an angle greater than 0° and less than or equal to 15°.

[0100] A plurality of wafer centering features 160 may also be provided in association with the shower pedestal 104. The wafer centering features 160, like the wafer support structure 138, may be generally positioned at a location about the first surface 106, e.g., about the first reference axis 116 and radially offset from the first reference axis 116. Specifically, the wafer centering features 160 may each have one or more centering surfaces 162, at least a portion of which is positioned a third distance 146 away from the first reference axis 116 in a direction perpendicular to the first reference axis 116 and faces the first reference axis 116. The third distance 146 may be, for example, in the range of 150.5 mm to 150 mm for a system processing 300 mm wafers. In some implementations, the wafer centering surfaces may have a portion that forms an angle of less than 45° with the first reference axis 116. In some further such embodiments, the wafer centering surface may have a portion that forms an acute angle with the first reference axis 116 that is greater than 0° and less than or equal to 30°.

[0101] The wafer centering feature 160 in Figures 1-3 is provided by a wheel 164, although other wafer centering features may be used, as discussed later in this specification. In the particular example of Figures 1-3, the wafer centering feature 160 is supported on a wheel riser structure 182 having a portion that can move up or down through a notch (not shown) or hole 184 in the shower pedestal 104. The wafer support structure 138 in this example is also penetrated with an opening that allows the wheel riser structure 182 to pass therethrough, although other embodiments may forgo such a feature.

[0102] The wheel riser structure 182 may be connected to one or more wheel riser support structures 180, such as, for example, annular rings extending around the stem 105. The wheel riser support structure 180 may be connected to one or more vertical lifting mechanisms 178, such as, for example, one or more linear actuators, which may be controllably actuated to move the one or more vertical lifting mechanisms 178 at least between a first configuration and a second configuration. The one or more vertical lifting mechanisms may support the wheel riser structure 182, and thus the wheels 164, as a whole. In the first configuration, at least a portion of each wheel is located farther from the first mean mid-plane 114 (or at least from a portion of the first mean mid-plane 114 that is disposed at a first distance 142 from the first mean mid-plane 114 and a second distance 144 from the first reference axis 116) than the wafer support surface 140. As shown in FIG. 3, the wheels 164 are positioned in a location that coincides with the one or more vertical lifting mechanisms 178 in the first configuration. As can be seen, approximately half of the wheels 164 are farther from the first average midplane 114 than the wafer support surface 140, but most of the wheels 164 may be farther as well (but at least some of the wheels 164 will still be).

[0103] The wafer 101 is shown in FIGS. 1-3 perfectly centered, for example centered on the first reference axis 116. However, if the wafer 101 is lowered onto the wafer support structure 138 slightly off-center from the first reference axis 116, the edge of the wafer 101 may rest on the wheel 164. Friction between the wheel 164 and the wafer 101, combined with the weight of the wafer 101, may create a torque on the wheel 164 that causes the wheel 164 to rotate clockwise (with respect to the orientation of FIG. 3). The wafer 101 may remain in contact with the wheel 164 as it rotates, causing the wafer 101 to move downward and radially inward toward the first reference axis 116. When the edge of the wafer 101 finally rests on the wafer support surface 140, the wafer will be centered on the first reference axis 116, or at least will be more centered on the first reference axis 116 than it was before the rotation of the wheels 164. If there are at least three wafer centering features 160 spaced apart at positions about the first reference axis 116, for example at angular intervals of about 120°, such wafer centering features 160 can act to center the wafer 101 regardless of in which direction the wafer 101 is misaligned with respect to the first reference axis 116.

[0104] When the one or more vertical lifting mechanisms 178 are in the second configuration, each wheel 164 may be located between the first mean mid-plane 114 and a location where that wheel 164 was located when the one or more vertical lifting mechanisms were in the first configuration, i.e., closer to the first mean mid-plane 114 than where that wheel 164 was located when the one or more vertical lifting mechanisms were in the first configuration. The dashed outlines of the wheels 164, wheel riser structures 182, and guide wheels 165 labeled "A" in FIG. 3 show exemplary locations of such components that coincide with the one or more vertical lifting mechanisms in the second configuration. However, it will be understood that such components may be similarly located in any of a number of other locations, for example, the wheels 164 may be positioned such that they are still located within the openings of the wafer support structure 138. For example, the wheels 164 may be positioned such that the portion of the wheels furthest from the first mean mid-plane is approximately at the same height as the portion of the wafer support structure furthest from the first mean mid-plane, or approximately at the same height as the wafer 101 (if present). In another example, the wheels 164 may be positioned such that the portion of the wheels 164 closest to the first mean mid-plane 114 is tangent to the first mean mid-plane 114 or at least very close to the first mean mid-plane 114.

[0105] It will also be appreciated that the wafer 101 may be initially placed on the wafer support structure 138 by the one or more vertical lifting mechanisms 178 in the second configuration, and then the one or more vertical lifting mechanisms 178 may be transitioned to the first configuration after the wafer 101 is on the wafer support structure 138. In such an embodiment, the wafer may be moved radially inwardly to become closer to being centered on the first reference axis 116 due to the upward movement of the wheels 164 resulting from such motion.

[0106] 1-3, the wheel riser structure 182 may incorporate one or more guide wheels 165. The guide wheels 165 may be configured to aid in positioning the wheel riser structure 182 relative to the wafer support structure 138 to more accurately position the wheels 164 relative to the first reference axis 116, thereby increasing wafer centering accuracy. The guide wheels 165 may contact an interior surface of an opening through the wafer support structure 138, for example, when the one or more vertical lifting mechanisms 178 transition from the second configuration to the first configuration, thereby causing a portion of the wheel riser structure 182 to translate within the opening in the wafer support structure 138. The illustrated embodiment features three guide wheels 165: one guide wheel 165 that rotates about an axis perpendicular to the page and guides the wheel riser structure 182 toward the first reference axis 116, and two guide wheels 165 positioned on either side of the wheel riser structure and rotate about axes parallel to the page. The latter two guide wheels 165 can act to guide the wheel riser structure 182 in a direction parallel to the axis of rotation of the other guide wheel 165 (i.e., perpendicular to the page). It will be appreciated that in some embodiments, a fourth guide wheel can also be included to guide the wheel riser structure 182 radially outward from the first reference axis 116, for example, if the wheel riser structure 182 is too close to the first reference axis 116. In some embodiments, the wheel 164 may serve such purpose and act as a guide wheel 165 when passing through an opening in the wafer support structure 138, while in other embodiments a separate guide wheel 165 may be provided for this purpose.

[0107] It will also be understood that fewer than three guide wheels 165 may be provided as well. For example, the two side guide wheels 165 (which rotate about axes perpendicular to the rotational axis of the wheels 164) may be omitted, possibly with little impact on centering performance, leaving only a single guide wheel 165 (or two guide wheels) to radially guide the wheel riser structure 182 toward or away from the first reference axis 116.

[0108] It will be further appreciated that the guide wheels 165 may also, or instead, be mounted on the underside of the wheel riser structure 182 to engage with an interior surface of a notch or hole 184 in the shower pedestal instead of or in addition to an interior surface of an opening in the wafer support structure 138. It will also be appreciated that the guide wheels 165 may be mounted within the shower pedestal 104 and / or wafer support structure 138 (and thus remain fixed in place but rotatable as the wheel riser structure 182 moves) and configured to contact the wheel riser structure 182 as it translates.

[0109] Additionally, as discussed above, some embodiments may not utilize any guide wheels 165, e.g., may not be guided (or at least not guided by contact with the wafer support structure 138 and / or shower pedestal 104).

[0110] In some implementations, the vertical lifting mechanism may be further configured to transition between at least the first and second configurations and a third configuration. When the one or more vertical lifting mechanisms are in the third configuration, the first mean mid-plane 114 may be disposed between the wafer support surface 140 and at least a portion of each wheel 164. In other words, the wheels 164 may be at least partially retracted below the height of the first mean mid-plane 114. The dashed outline of the wheels 164, wheel riser structure 182, and guide wheels 165, labeled "B" in FIG. 3, shows an exemplary location of such components consistent with the one or more vertical lifting mechanisms in the third configuration. In some such implementations, the first mean mid-plane 114 may be disposed between the wafer support surface 140 and all of each wheel 164, e.g., each wheel 164 may be fully retracted into the shower pedestal 104. In FIG. 3, the white double-headed arrows indicate predicted movements or transitions between a first configuration and a second configuration, and between the second configuration and a third configuration.

[0111] It will be appreciated that in some implementations, the one or more vertical lifting mechanisms 178 may only transition between the first and second configurations with the wheels 164 disposed at least partially between the first mean mid-plane 114 and a plane that is coplanar with, for example, the underside of the wafer 101 during a wafer processing operation. In other implementations, the one or more vertical lifting mechanisms 178 may further transition from the second configuration to a third configuration to retract the wheels 164 completely into the shower pedestal 104, which may better protect the wheels 164 (e.g., from exposure to potential deposition or etch gases that may affect wafer centering accuracy by changing the diameter of the wheels 164).

[0112] The ability to move the wheels 164 between various heights relative to the first mean mid-plane 114 and the first surface 106 allows the wheels 164 to be used to help center the wafer 101 while being moved out of the way to facilitate wafer processing operations. For example, once the wafer 101 is placed and centered on the wafer support structure 138, the shower pedestal 104 can be moved upward to approach a showerhead (not shown) disposed above the shower pedestal. In some cases, the showerhead can support a ring structure, e.g., a focus ring, that can be configured to rest on and be supported by the wafer support structure 138 when the shower pedestal is brought sufficiently close to the showerhead. Such a ring structure can be generally annular in shape and can have an inner edge with a radius less than the diameter of the wafer so as to overlap the outer edge of the wafer. By making the wheel riser structure 182 movable / retractable, the wheel 164 can be moved to a lower position relative to the wafer support structure 138 prior to or in parallel with the movement of the shower pedestal 104 to bring the ring structure into contact with the wafer support structure 138. This avoids potential interference / contact between the wheel 164 and / or the wheel riser structure 182 and the ring structure and / or the showerhead. Also, possible radial flow conductance changes (in either or both the wafer-to-showerhead space or the wafer-to-shower pedestal space) around the periphery of the wafer due to the presence of the wheel riser structure 182 and / or the wheel 164 are avoided or reduced.

[0113] Various types of wafer support structures 138 and wafer centering features 160 can be used in various embodiments. Figures 4-7 show four examples of such elements to teach various types of such structures, but it will be recognized that other variations of such structures are within the scope of the present disclosure as well. Wafer 101 is shown as a portion of a shaded, transparent circle in Figures 4-7 for reference.

[0114] Figure 4 shows an isometric detail view of the embodiment of wafer centering feature 160 and wafer support structure 138 shown in Figures 1-3, and Figure 4' shows the same embodiment, but with wheels 164 retracted into shower pedestal 104 (e.g., as may be the case when one or more vertical lifting mechanisms 178 are in the third configuration). Thus, many of the elements shown have already been described above.

[0115] As can be seen more clearly in FIG. 4, some embodiments of the wafer support structure 138 may generally have two main parts: a riser portion or structure 150 and a cantilever portion or structure 148. The riser structure 150 and the cantilever structure 148 may be provided by separate components or may be different parts or portions of a single component as shown. The cantilever structure 148 may be supported relative to the shower pedestal 104 by the riser structure 150. A proximal end 152 of the cantilever structure 148 may be connected to the riser structure 150, and the wafer support surface 140 of the wafer support structure 138 may be disposed at a distal end 154 of the cantilever structure 148. The cantilever structure 148 may generally have a long axis 158 oriented toward / away from the first reference axis 116, for example along a radius extending from the first reference axis 116. In some embodiments, the cantilever structures 148 may extend radially inward from a corresponding riser structure 150 toward the first reference axis 116 .

[0116] The opening 186 through the cantilever structure 148 of the wafer support structure 138 is more clearly seen in Figure 4'. As can be seen, the opening 186 is sized to allow the wheel riser structure 182 and the wheel 164 to pass at least partially through the opening 186, thereby allowing the wheel 164 to be moved to a position (as shown in Figure 4) where the wheel 164 can contact the wafer 101 and act to center the wafer 101 on the first reference axis 116.

[0117] The wafer support surface 140 and the centering surface 162 are also seen more clearly in Figure 4. In the case of the wheel 164, the centering surface 162 may actually be the entire circular outer surface of the wheel 164, but generally only the portion of that surface closest to the first reference axis 116 may actually act to center the wafer 101. As the wheel 164 rotates about the axis 166, various portions of the outer surface of the wheel 164 may act as the centering surface 162.

[0118] Another feature seen more clearly in Figures 4 and 4' is a channel 156 provided in a side or surface of the cantilever structure 148 facing away from the first mean mid-plane 114. In some implementations, the channel 156 may be provided in the cantilever structure 148, or more generally in the wafer support structure 138, to help prevent or reduce particle contamination of the wafer 101 when the wafer support structure 138 is used to support a ring structure as discussed above. The channel 156 may generally be located farther from the first reference axis than the wafer support surface 140, for example between the wafer support surface 140 and at least a portion of the riser structure 150, and may extend in a direction transverse to the major axis 158 and parallel to the first mean mid-plane 114. When the wafer support structure 138 is used to support a ring structure, such as a focus ring, the channel 156 may receive an annular wall that may protrude from a lower surface of the ring structure. The channel 156 may be dimensioned so as not to contact the annular wall, and the wafer support structure 138 may be configured to contact the ring structure at a location outside of the annular wall. Any particles that arise through contact between the ring structure and the wafer support structure 138 may thus be prevented by the annular wall from having a direct path of travel to the wafer. This may act to reduce the opportunity for such particles to reach the wafer and potentially contaminate it, or to prevent such entirely. The channel 156 may be at least 0.75 mm or at least 1 mm deep, in some implementations, on one or both ends of the channel 156.

[0119] 1-4' feature wafer centering feature 160 and wafer support structure 138 disposed at the same angular position about first reference axis 116. As a result, wheel riser structure 182 is generally required to pass through cantilever structure 148 via aperture 186 (although a notch may be used in place of aperture 186, if desired). However, wafer centering feature 160 does not necessarily need to be disposed at the same angular position about first reference axis 116 as wafer support structure 138.

[0120] FIG. 5 illustrates an exemplary embodiment in which the wafer centering feature 560 is circumferentially offset, i.e., has a different angular position relative to the first reference axis 516 than the wafer support structure 538. FIG. 5' illustrates the same embodiment as FIG. 5, but with the wheel riser structure 582 recessed into the shower pedestal 504. Many of the structures and features illustrated in FIG. 5 and FIG. 5' are generally similar to the structures and features illustrated in FIG. 1 through FIG. 4'. Thus, the descriptions and discussion of such structures and features provided above with respect to FIG. 1 through FIG. 4' may be understood to be equally applicable to the corresponding structures and features in FIG. 5 and FIG. 5', unless otherwise indicated or suggested by the following discussion. Such corresponding structures and features in FIG. 5 and FIG. 5' are illustrated using reference numbers having the same last two digits as those used in the reference numbers of such structures or features in FIG. 1 through FIG. 4'.

[0121] As shown in FIG. 5, the wafer support structure 538 is circumferentially offset from the wheel riser structure 582, i.e., at a different angular position than the wheel riser structure 582 with respect to a first reference axis (not shown, but see previous figures). Thus, the notch or hole 584 through the shower pedestal 504 is located at a different location relative to the wafer support structure 538 than it is located in FIG. 4' (for clarity, the dashed line extending radially outward from the hole 584 shows an example where material of the shower pedestal 504 may be removed or omitted to turn the hole 584 into a notch). Furthermore, the wafer support structure 538 in this example no longer has an opening such as the opening 186 through it, since it is no longer the case that the wheel riser structure passes through the cantilever structure of the wafer support structure 538. The channel 556 may also be more discernible in FIG. 5 and FIG. 5', and shading has been added to better highlight its extent.

[0122] In the above examples, the wafer centering features are provided by wheels that can be moved vertically through the use of one or more vertical lifting mechanisms. However, in some embodiments, the wafer centering features used can be supported by the wafer support structure (at least for vertical movement) and fixed via a gap to the wafer support structure. FIG. 6 shows an example of such an embodiment. Many of the structures and features shown in FIG. 6 are generally similar to the structures and features shown in FIGS. 1 through 5′. Thus, the descriptions and discussion of such structures and features provided above with respect to FIGS. 1 through 5′ can be understood to be equally applicable to the corresponding structures and features in FIG. 6, unless otherwise indicated or suggested by the following discussion. Such corresponding structures and features in FIG. 6 are shown using symbols having the same last two digits as those used in the symbols of such structures or features in FIGS. 1 through 5′.

[0123] 6, the wheels 664 are supported by the wafer support structure 638 rather than by a wheel riser structure. As a result, the wheels 664 remain at a constant height relative to the wafer support structure 638, e.g., permanently in a position similar to the position the wheels 164 reside in when the one or more vertical lifting mechanisms 178 discussed above are in a first configuration.

[0124] In some implementations, the wafer centering feature may be provided by a non-wheel structure. For example, the wafer centering feature may instead be a static structure, such as a protrusion, having an inclined surface, such as a structure having an inclined surface that provides the centering surface. Figure 7 shows an exemplary embodiment of a wafer support structure 738 having a wafer centering feature including a protrusion, the protrusion extending upward from a wafer support surface 740 and having an inclined surface that provides a centering surface 762.

[0125] Many of the structures and features in Figure 7 are generally similar to the structures and features shown in Figures 1 through 5'. Accordingly, the descriptions and discussion of such structures and features provided above with respect to Figures 1 through 5' may be understood to be equally applicable to the corresponding structures and features in Figure 7, unless otherwise indicated or suggested by the above discussion. Such corresponding structures and features in Figure 7 are designated using reference numerals having the same last two digits as used in the reference numerals of such structures or features in Figures 1 through 5'.

[0126] It will also be appreciated that a static wafer centering feature, such as that shown in FIG. 7, may also be implemented in place of the wheels on the wafer centering feature with a wheel riser structure (or, more appropriately, a static feature riser structure similar to the wheel riser structure) that can be moved up and down via one or more vertical lifting mechanisms.

[0127] In embodiments where the wafer centering feature cannot be raised or lowered relative to the wafer support structure, the wafer centering feature may protrude into a space that may need to be occupied by other components during some stages of operation. Such other components may include, for example, a focus ring and / or a showerhead.

[0128] FIG. 8 shows a view of an example shower pedestal 804, as well as a showerhead 828 and a focus ring 870. In FIG. 8, a wafer is not shown. In FIG. 8, the showerhead 828 is not shown in its normal position above the shower pedestal 804, but instead has been flipped upside down and relocated to the side of the shower pedestal 804, as if the shower pedestal 804 and showerhead 828 were the covers of an open book. A focus ring 870 is shown supported by the wafer support structure 838 (although in some implementations the focus ring 870 may be captured within features of the showerhead 828 such that it generally cannot be positioned separately from the showerhead as shown).

[0129] Many of the structures and features illustrated in Figure 8 are generally similar to the structures and features illustrated in Figures 1-3, although the wafer support structure 838 and wafer centering features utilized are similar to those illustrated in Figure 6. Accordingly, the descriptions and discussion regarding such structures and features provided above with respect to Figures 1-3 and 6 may be understood to be equally applicable to the corresponding structures and features in Figure 8, unless otherwise indicated or suggested by the discussion below. Such corresponding structures and features in Figure 8 are designated using reference numbers having the same last two digits as used in the reference numbers of such structures and features in Figures 1-3 and 6.

[0130] 8, the showerhead 828 has a number of second gas distribution ports 830 distributed across a second surface 836 of the showerhead 828. The second gas distribution ports 830 can be used to distribute a process gas across the wafer (if present) during a processing operation. Such a process gas can, in some implementations, be a noble gas (e.g., argon (Ar)) or nitrogen (N) that can protect the top surface of the wafer from potential exposure to the process gas used to process the bottom surface of the wafer. 2 The gas may be a non-reactive gas such as

[0131] Focus ring 870 may be designed to overlap the edge of the wafer (if present) to provide a mechanical barrier against potential diffusion of process gases from the bottom surface of the wafer to the top surface of the wafer. Focus ring 870 may have an inner edge 872 and an outer edge 874 that are nominally circular. In some implementations, the inner edge may have a diameter less than twice the third distance (between the centering surface and the first reference axis, e.g., less than the diameter of the wafer) and the outer diameter may have a diameter greater than twice the third distance.

[0132] As can be seen in FIG. 8 , both focus ring 870 and showerhead 828 include features provided to accommodate the presence of wafer centering feature 860, such as the presence of the portion of wafer support structure 838 supporting wheel 864 and its axle, that protrudes above a height where the top of the wafer would normally be located.

[0133] Focus ring 870 has an opening 876 that is proximate inner edge 872 and sized large enough to allow protruding portions of wheel 864 and wafer support structure 838 to pass through opening 876 without contacting focus ring 870 when focus ring 870 is supported by wafer support structure 838. Opening 876 may also be a notch extending outwardly from inner edge 872 (as suggested by the dotted line seen between opening 876 and inner edge 872 in the enlarged detail view shown). Showerhead 828 similarly has a number of recesses 868, the number of recesses 868 corresponding to the number of wafer centering features 860 used, e.g., three. Recesses 868 are positioned such that portions of wafer centering features 860 that may protrude through focus ring 870 can extend into the recesses, thereby preventing showerhead 828 from reaching its lowest position and contacting wafer centering features 860. The recesses 868 and / or openings 876 may generally be positioned such that a second reference axis (not shown) that is parallel to the first reference axis 816 and passes through the center of, for example, the wheel 864 or other wafer centering feature, such as a protrusion as shown in FIG. 7, also passes through the corresponding opening 876 and / or recess 868.

[0134] For further clarity, reference is made to FIG. 9, which shows showerhead 828 and shower pedestal 804 of FIG. 8 positioned as they would be during an actual wafer processing operation (the wafer is not shown in the main view, but is shown in dotted and cross-hatched lines in the detailed view). As seen in the figure, focus ring 870 is supported by wafer support structure 838. A ring support collar 871 that extends around showerhead 828 has a flange that extends inwardly toward focus ring 870. The flange may have an inner diameter slightly smaller than the inner diameter of focus ring 870, which allows focus ring 870 to rest on the flange and thus be indirectly supported by showerhead 828 when not supported by wafer support structure 838. The distance between the surface of the flange supporting focus ring 870 and the underside of showerhead 828 may be dimensioned to be greater than the thickness of the portion of focus ring 870 that rests on the flange, thereby allowing focus ring 870 to be free to move vertically over a limited range of motion. This can ensure that focus ring 870 can rest completely on wafer support structure 838, which can allow the gap between focus ring 870 and wafer 801 to be more tightly controlled.

[0135] As can be seen in FIG. 9 , recess 868 is positioned and dimensioned such that when focus ring 870 rests on wafer support structure 838, wheel 864 can extend into recess 868 without contacting showerhead 828.

[0136] Also seen in Figure 9 is a second plenum 832 that fluidly connects to the second gas distribution port 830 by a second gas inlet 834. The second gas inlet 834 can be used to introduce one or more process gases into the showerhead 828 for distribution across the top of the wafer 801. The stem 805 of the shower pedestal 804, the first gas inlet 812, and the first gas distribution port 808 are also shown in Figure 9.

[0137] FIG. 10 shows an example of a shower pedestal 1004 including a showerhead 1028 and a wafer support structure 1038 similar to that shown in FIG. 4 and FIG. 4'. The structure shown in FIG. 10 is cut away to show two orthogonal cross-sectional planes of the wafer support structure 1038 connected to the shower pedestal 1004. Many of the structures and features shown in FIG. 10 are generally similar to the structures and features shown in the previously discussed figures. Thus, the descriptions and discussions regarding such structures and features provided above with respect to other figures can be understood to be equally applicable to the corresponding structures and features in FIG. 10 unless otherwise indicated or suggested by the following discussion. Such corresponding structures and features in FIG. 10 are shown using symbols having the same last two digits as used in the symbols of such structures and features in the previous figures.

[0138] The illustrated shower pedestal 1004 has a first plenum 1010 that can provide one or more process gases to an underside of the wafer 1001 via a plurality of first gas distribution ports 1008. Such process gases can be provided to the shower pedestal 1004 via a first gas inlet disposed in the shower pedestal stem 1005. The wafer 1001 can be supported on a plurality of wafer support structures 1038, such as wafer support structures similar to the wafer support structure 138 discussed above. Such wafer support structures 1038 can have an opening 1086 that allows the wheel riser structure 1082 and the wheel 1064 (shown here recessed into a hole 1084 in the shower pedestal 1004) to be extended therethrough to center or better center the wafer 1001 on a first reference axis (not shown here, but see previous discussion regarding first reference axis for other embodiments).

[0139] 10 has a second plenum 1032 through which one or more process gases (which may be inert or non-reactive with respect to the process gases that may be delivered from the shower pedestal 1004) may be provided. The second plenum 1032 may be provided with such one or more process gases through a second gas inlet 1034 disposed in the showerhead stem 1029, which may then flow such process gases toward the top surface of the wafer 1001 through a second gas distribution port 1030.

[0140] 10, the focus ring 1070 can rest on the ring support collar 1071 when the shower pedestal 1004 is low enough that it cannot rest on the wafer support structure 1038. When the shower pedestal 1004 is high enough, the focus ring 1070 can rest on the wafer support structure 1038. The wafer support structure 1038 can have, for example, tapered sides (as shown) that can serve as the ring support surface 1075. The ring support surface 1075 can contact, for example, a similarly sloped side on the underside of the focus ring 1070, for example, the focus ring 1070 can have recesses or pockets 1067 on its bottom surface positioned to align with the wafer support structure 1038, and the sides of these recesses or pockets can be sloped to engage the sloped sides of the wafer support structure 1038. Such angled ring support surfaces 1075 may act to center the focus ring 1070 on the first reference axis when the focus ring 1070 rests on the wafer support structure 1038. For example, the set of opposing angled ring support surfaces 1075 for each wafer support structure 1038 may be symmetrical about a plane that is coplanar with the first reference axis, thereby causing corresponding mating features on the focus ring to be centered on the plane of symmetry when placed in contact with the ring support surfaces 1075. If three sets of opposing angled ring support surfaces 1075 are disposed about the first reference axis, the resulting centering effect may cause the focus ring to center itself on the first reference axis (and thus the wafer 1001).

[0141] FIGURE 10 also shows an annular wall 1077 on the underside of focus ring 1070. The annular wall may extend downwardly into a channel (not numbered, see previous embodiments) in the cantilever structure of wafer support structure 1038, as previously described. As can be seen in FIGURE 10, any particles that arise through contact between ring support surface 1075 and focus ring 1070 are prevented by annular wall 1077 from having a direct path to wafer 1001.

[0142] As mentioned above, shower pedestals such as those described above can have other numbers of wafer support structures. For example, while FIGS. 1, 2, and 8-10 show an exemplary shower pedestal having three wafer support structures, other embodiments may have different numbers of wafer support structures. For example, FIG. 11 shows an isometric view of a shower pedestal 1104, which is similar to shower pedestal 804, except that it has four wafer support structures 1138 (compared to the three wafer support structures 838 of shower pedestal 804). Although an embodiment including three wafer support structures may provide an inherently stable support for a wafer supported thereby, an embodiment such as shower pedestal 1104 may be better adapted to support a wafer 1101 that may exhibit symmetry about two orthogonal axes. For example, some semiconductor processing operations may cause a wafer to bend about two orthogonal axes, resulting in the wafer assuming a saddle-like shape. As a result, the periphery of such a wafer may have "high" points at diametrically opposed locations, e.g., at 0° and 180°, and "low" points at two other diametrically opposed locations 90° out of phase from the high points, e.g., at 90° and 270°. The shower pedestal 1104 has four wafer support structures 1138 and thus may be used to support such a wafer at locations between the high and low points along the wafer edge (which may generally all be at the same height).

[0143] It will be understood that all of the embodiments discussed and illustrated in the figures herein that exhibit three-fold radial symmetry (e.g., having three wafer support structures) may also be provided in an embodiment having four-fold radial symmetry, for example as illustrated by the shower pedestal 1104.

[0144] The shower pedestal and showerhead arrangements described above may be implemented in the context of single-station or multi-station semiconductor processing chambers. FIG. 12 illustrates an exemplary four-station semiconductor processing tool. The illustrated tool may include a chamber 1202 including a rotary indexer 1288 that may be controllable to rotate about a first axis of rotation 1292. The rotary indexer 1288 may have a plurality of forks 1290 arranged in a circular array about the first axis of rotation 1292 such that when the rotary indexer 1288 is rotated about the first axis of rotation 1292, the forks 1290 are also rotated about the first axis of rotation 1292. Four sets of shower pedestals 1204 and showerheads 1228 are also arranged in a circular array about the first axis of rotation 1292. The rotational indexer 1288 may generally be configured to rotate between various rotational positions, such as a first rotational position in which a wafer lifting surface of a first of the forks 1290 is positioned above a first of the shower pedestals, a second rotational position in which a wafer list surface of the first fork 1290 is positioned on a second of the shower pedestals, etc.

[0145] The chamber 1202 can have multiple wafer loading slots 1203, which can provide, for example, an access point for introducing or removing wafers into or from the chamber 1202. A rotary indexer 1288 can be used to rotate wafers introduced into the chamber 1202 between the various shower pedestals 1204. In embodiments including only a single station, the chamber 1202 can be sized accordingly small and only one shower pedestal 1204 and showerhead 1228 can be disposed within the chamber 1202. The rotary indexer 1288 and fork 1290 can also be omitted.

[0146] FIG. 13 shows a perspective view of an exemplary fork 1290 containing a wafer 1201 (shown in a see-through manner so that the features of the fork 1290 can be seen through it). As seen in FIG. 13, the fork 1290 has two arms 1296 that extend outwardly from a hub or spindle of a rotary indexer 1288 (not shown). The arms 1296 may extend at least partially around a circular region 1299 having a diameter dimensioned to be twice a third distance (a third distance as discussed above with respect to other embodiments, e.g., a distance that is the same or nearly the same as the radius of a wafer to be handled using the forks). In some embodiments, the arms 1296 may be located completely outside of the circular region 1299. For example, the circular region 1299 may be positioned relative to the fork 1290 such that the circular region 1299 is centered on the first reference axis 1216 when the rotational indexer 1288 is controlled to position the fork 1290 of FIG. 13 in a first rotational position with the wafer list surface of the fork 1290 positioned above a first one of the shower pedestals 1204, for example in a position where the wafer 1201 supported by the fork 1290 would theoretically be centered on its first reference axis.

[0147] The arm 1296 may include one or more protrusions 1298 that extend partially into the circular region 1299 toward the first reference axis 1216. The protrusions 1298 may be adjacent to the arm 1296 and may each have a wafer lifting surface 1294 that is located at a non-parallel angle to the first mean mid-plane. It will be appreciated that the wafer lifting surfaces 1294 may also extend at least partially into the circular region 1299. The wafer lifting surfaces 1294 may be inclined, for example, at an angle greater than 0° and less than or equal to 25° relative to the first mean mid-plane. This allows the forks 1290 to contact the wafer 1201 only along the edge of the wafer 1201, thereby minimizing the amount of contact between the bottom surface of the wafer 1201 and the forks 1290 and reducing the magnitude of potential particle generation that may occur.

[0148] The various components described above may be made from a variety of suitable materials, such as materials that are non-reactive or inert to the various process gases that may be used. For example, one or more of the wheels (if used), static wafer centering features (if used), wafer support structures, riser structures of the wheels or static structures (if used), focus rings, shower pedestals, showerheads, and forks (if used) may be made in whole or in part from ceramic materials such as aluminum oxide, silicon nitride, and the like.

[0149] Figures 14 through 26 show a four station arrangement similar to that shown in Figure 12 during various stages of a wafer installation and positioning operation. In many (but not all) of Figures 14 through 26, the showerhead 1228 closest to where the wafer loading slot 1203 is located has been omitted from the view so as not to obscure the shower pedestal 1204 positioned therebelow. The chamber 1202 has also been omitted from all of Figures 14 through 26 to avoid obscuring the features being discussed.

[0150] In FIG. 14, two end effectors 1291 are shown supporting a wafer 1201. The end effectors 1291, like the forks 1290, may have wafer lifting surfaces inclined at an oblique angle relative to a first mean midplane or a first reference axis of the shower pedestal 1204. The end effectors 1291 may be attached to one or more robot arms (not shown), which may be controlled to insert the end effectors 1291 and the wafer 1201 supported thereby into the chamber 1202 via the wafer loading slot 1203, as shown in FIG. 15. In FIG. 15, the wafers 1201 are each nominally centered on a corresponding one of the shower pedestals 1204 (the showerheads 1228 corresponding to these two shower pedestals 1204 are not shown in FIGS. 14-20).

[0151] 16, lift pins 1218, supported by lift pin support structure 1222, have been extended by one or more lift pin actuators (not shown, but see FIG. 14) out of the first surface of shower pedestal 1204 on which wafer 1201 rests, thereby lifting wafer 1201 off end effector 1291. As can be seen, wafer 1201 no longer rests on the wafer lifting surface of end effector 1291.

[0152] In FIG. 17, the robot arm or arms have been retracted from the chamber 1202 leaving the wafer 1201 (supported by lift pins 1218) within the chamber 1202. As seen in the detailed inset 17', there are multiple wafer support structures 1239 positioned at locations on each shower pedestal 1204 similar to those discussed above with respect to FIGS. 1-3. However, it will be understood that any suitable wafer support structure 1238 capable of assisting in wafer edge contact may be used, including but not limited to the examples discussed above herein with respect to FIGS. 4-7. In this particular example, the wafer centering features (wheel and wheel riser structures that can be extended or retracted from the shower pedestal 1204) are shown retracted within the shower pedestal 1204.

[0153] 18, the lift pin actuators are controlled to lower the wafer 1201 onto the wafer support structure 1238 by retracting the lift pins 1218 back into the shower pedestals 1204. At this point, the wafer 1201 is nominally centered on each shower pedestal 1204, but could still benefit from additional centering.

[0154] In FIG. 19, one or more vertical lifting mechanisms (not shown, but see FIG. 14) move the wheel riser support structure 1280 vertically upward, thereby extending the wheel riser structure 1282 and wheels 1264 upward out of the shower pedestal 1204 and through openings in the wafer support structure 1238. During such movement, one or more of the wheels 1264 (see detailed FIG. 19′) can contact an edge of the wafer 1201 and exert a radially inwardly directed force on the wafer 1201, which causes the wafer 1201 to become more centered on a first reference axis (not shown, but see previous figures) for the corresponding shower pedestal 1204, if it is not already properly centered. As previously mentioned, in some embodiments, one or more vertical lifting mechanisms can be actuated to raise the wheel riser structure 1282 and the wheels 1264 prior to retraction of the lifting pins 1218 so that the wafer 1201 comes into contact with the wheels 1264 as the lifting pins 1218 lower the wafer 1201 onto the wafer support structure 1238.

[0155] In FIG. 20, one or more vertical lifting mechanisms have been actuated to lower the wheel riser structure 1282 and wheels 1264 back into the shower pedestal 1204, thereby leaving the wafer 1201 resting on the wafer support structure 1238 in a position that is centered or more centered on the first reference axis of the shower pedestal 1204.

[0156] In FIG. 21, the shower pedestal 1204 has been raised (and / or the shower head 1228 has been lowered), e.g., by a corresponding lifting mechanism (not shown), to reduce the gap between the upper surface of the wafer 1201 and the lower surface of the shower head 1228. Although not shown, the gap between the lower surface of the shower head 1228 and the upper surface of the wafer 1201 may be reduced to an extent that a focus ring supported by the shower head 1228 may contact the wafer support structure and then be supported by the wafer support structure at a desired distance from the wafer 1201 (see, e.g., FIG. 10). One or more process gases may then be flowed from the shower pedestal 1204 toward the underside of the wafer 1201, e.g., through actuation of one or more valves, for one or more time periods, such that material may be deposited on or etched from the underside of the wafer 1201. At the same time, a non-reactive or inert gas, e.g., a noble gas such as argon or a gas such as nitrogen, can be flowed through showerhead 1228 onto the top surface of wafer 1201 and focus ring to prevent undesired deposition or etching from occurring on the top surface of wafer 1201.

[0157] As shown in FIG. 22, once processing operations for a wafer 1201 at a given station are completed, the shower pedestal 1204 can be retracted (and / or the showerhead 1228 can be raised) to return the semiconductor processing tool to a state similar to that shown in FIG. 20.

[0158] The indexer lifting mechanism (not shown) may then be directed to move the forks 1290 vertically upward, as shown in Figure 23. Thus, the forks 1290, which may be nominally located in an arcuate recess in the exterior of the shower pedestal 1204, as shown in Figure 23, may rise to contact the edge of the wafer 1201 with their respective wafer lifting surfaces 1294. Continued upward movement of the forks 1290 may then cause the wafer 1201 to be lifted off of their corresponding wafer support structures 1238, such that the wafer 1201 is now fully supported by the forks 1290, and the forks 1290 and wafer 1201 are not in danger of colliding with either structure when the rotary indexer 1288 is rotated.

[0159] In Figure 24, the rotary indexer 1288 has been controlled to rotate 45°, thereby rotating the fork 1290 and wafer 1201 supported by the rotary indexer 1288 halfway to the next station. In Figure 25, the rotary indexer 1288 has completed its rotation, and the wafer 1201 is now positioned directly above a different shower pedestal 1204 than it was located immediately prior to such movement.

[0160] 25, the rotary indexer 1288 is controlled to move vertically downward, thereby causing the wafers 1201 to be placed on the wafer support structures 1238 of the shower pedestal 1204 to which they have been transferred. Following or preceding such placement, the wafer centering feature may be extended to center the wafers 1201 relative to the first reference axis of the station to which each wafer 1201 has been transferred, for example as shown in FIG.

[0161] As seen in Figures 14 through 25, all three systems that support the wafer 1201 during placement / retrieval from the tool, processing within the tool, and transfer between stations within the tool are designed to contact the wafer 1201 via edge contact only. This reduces or eliminates the potential risk of particle generation and also reduces or eliminates any "shadowing" effects that may occur near the wafer edge during processing operations (potential later damage that may occur through contact between the recently processed surface of the wafer 1201 and features that would otherwise contact the underside of the wafer at a non-edge location).

[0162] 27 shows a simplified schematic diagram of a semiconductor processing tool having features and systems such as those described above. As shown, a chamber 2702 includes a number of shower pedestals 2704 and showerheads 2728 (examples of which are labeled on one side but not on the other; it will be understood that the embodiment shown is symmetrical with respect to the components shown).

[0163] The chamber 2702 also includes a rotary indexer 2788. The rotary indexer 2788 may be supported by a rotary drive 2789 (e.g., an electric motor), which may be supported by a vertically oriented linear drive system 2787. The linear drive system 2787 may be configured to translate the rotary drive 2789 up and down, and to rotate the rotary drive in a clockwise or counterclockwise direction, in response to input received from a controller 2795. The controller 2795 may also be operatively connected to, e.g., directly or indirectly connected to, a vertical lifting mechanism 2778, e.g., a linear actuator, a screw drive, a pneumatic actuator, etc., and a lifting pin actuator 2720, e.g., a linear actuator, a screw drive, a pneumatic actuator, etc., such that they may be controlled. The vertical lifting mechanism 2778 may be configured to raise or lower the wheel riser support structure 2780 (and the wafer centering features supported thereby) in response to signals received from the controller 2795, while the lifting pin actuator 2720 may be configured to raise or lower the lifting pin support structure 2722 (and the lifting pins supported thereby) in response to signals received from the controller 2795.

[0164] 27, each of which may be operatively connected to a controller 2795, such that the controller 2795 can adjust the spacing between the shower pedestal 2704 and the showerhead 2728 by actuating either or both of the showerhead vertical drive 2727 and the shower pedestal vertical drive 2707 up and / or down in response to signals received from the controller 2795. In some implementations, one of the showerhead vertical drive 2727 and the shower pedestal vertical drive 2707 may be omitted leaving the other to still allow adjustment of the showerhead 2728 / shower pedestal 2704 spacing.

[0165] The controller 2795 may also be operatively connected to one or more first valves 2711 and one or more second valves 2733. The one or more first valves 2711 may be fluidly connected to one or more first gas sources 2709 and a first plenum of the shower pedestal 2704. The controller 2795 may be configured to control the one or more first valves 2711, for example, by providing associated control signals to the one or more first valves 2711, for example, to cause one or more first process gases to be delivered from the one or more first gas sources 2709 to the shower pedestal 2704.

[0166] Similarly, one or more second valves 2733 may be fluidly connected to the one or more second gas sources 2731 and to a second plenum of the showerhead 2728. The controller 2795 may be configured to control the one or more second valves 2733, for example, by providing associated control signals to the one or more second valves 2733, to cause one or more second process gases to be delivered from the one or more second gas sources 2731 to the showerhead 2728.

[0167] In some embodiments, a rotary indexer having forks that can be transitioned between open and closed states can be used in such a tool. Figures 28-31 show views of an indexer including openable / closable forks. Figure 28 shows the indexer 2888 in a closed state, while Figure 29 shows the same indexer 2888 in an open state. Figure 29 shows the indexer 2888 in an exploded view, and Figure 30 shows the indexer 2888 in both the open and closed states (the open state is shown in dashed lines).

[0168] As seen in FIGS. 28-31 , the indexer 2888 may include a fork that splits into a first half and a second half, e.g., a first half 2890a and a second half 2890b. Each pair of the first half 2890a and the second half 2890b may together provide a fork structure configured to support a semiconductor wafer when the rotary indexer 2888 is in a closed state. The first half 2890a may be attached to or be an integral part of a first hub 2893a, while the second half 2890b may be attached to or be an integral part of a second hub 2893b. The first hub 2893a may be connected to a first shaft 2897a, while the second hub 2893b may be connected to a second shaft 2897b. The second shaft 2897b may be hollow to allow the first shaft 2897a to pass through it, such that the first shaft 2897a and the second shaft 2897b are arranged coaxially to allow each to be driven independently, for example by two motors (not shown) with coaxial outputs, or other mechanism that allows each shaft 2897a and 2897b to be driven independently.

[0169] The first half 2890a, the first hub 2893a, and the first shaft 2897a may all be configured to rotate as a unit in response to rotation of the first shaft 2897a. Similarly, the second half 2890b, the second hub 2893b, and the second shaft 2897b may all be configured to rotate as a unit in response to rotation of the second shaft 2897b. When the first shaft 2897a and the second shaft 2897b are both rotated in the same direction at the same speed, the rotational indexer 2888 rotates without changing the position between the first half 2890a and the second half 2890b. However, if the first shaft 2897a and the second shaft 2897b rotate in opposite directions or potentially in the same direction at different speeds, the rotational position of the first hub 2893a relative to the second hub 2893b, and therefore the rotational position of the first half 2890a relative to the second half 2890b, can be changed. This allows the first half 2890a and the second half 2890b to be transitioned between an open state (shown in FIG. 29) and a closed state (shown in FIG. 28). In FIG. 31, the arrows indicate the opposite rotation between the first shaft 2897a and the second shaft 2897b, which results in the transition of the first half 2890a and the second half 2890b from an open state to a closed state. Of course, opposite amounts of opposite rotation will result in the opposite transition.

[0170] 28-31 may be used in any of the embodiments discussed herein, for example, in place of rotary indexer 2788 or rotary indexer 1288, as previously described. Rotary indexer 2888 may allow for greater separation between the wafer and pedestal and first and second halves 2890a and 2890b in the open state than would be allowed by a fixed fork. This may allow the forks (first and second halves 2890a and 2890b) to be positioned further away from the wafer and the pedestal that supports them during processing, thereby reducing the likelihood that first and second halves 2890a and 2890b will interfere with the processing of the wafer.

[0171] One problem that may arise in a system where a wafer can be supported such that it is suspended above a shower pedestal is that the wafer may flex slightly under its own weight. FIG. 32 shows an example of such wafer flexure, but it is heavily exaggerated. As shown in FIG. 32, a wafer 3201 is supported on a shower pedestal 3204. FIG. 33 shows a side view of the shower pedestal and wafer of FIG. 32. The wafer 3201 is supported through contact between the outer edge of the wafer and a number of, e.g., three, wafer support structures 3238. The dashed circle 3201′ represents a planar circle the same size as the wafer 3201, e.g., where the wafer 3201 would be if the wafer 3201 was very stiff and not subject to any flexure. As can be seen in the figures, the wafer 3201 conforms to the planar circle 3201' where the wafer 3201 is supported by each of the three wafer support structures 3238, but then sags or bows an amount Δ between the wafer support structures 3238, as shown in FIG. 33. As noted above, the bowing shown is greatly exaggerated in these figures (and other figures discussed below). This was done to make the bowing easily discernible. However, it will be appreciated that in actual practice, the amount of bowing Δ present may be on the order of only tens to hundreds of microns (for a 300 mm diameter wafer) and may not be easily perceptible to the human eye.

[0172] As discussed above, a ring-like structure, such as focus ring 870, may be centered on and placed on the wafer 3201. Such a ring-like structure may, for example, overlap the outer periphery of the wafer 3201 by a small amount. The ring-like structure may act as a diffusion barrier that prevents process gases introduced to the underside of the wafer 3201 from diffusing upward past the edge of the wafer 3201 into the region between the wafer 3201 and the showerhead (not shown, but see previous figures and discussion) through which purge gas may flow. The ring-like structure may contact the wafer 3201 around its outer edge or may be positioned such that there is a small gap, e.g., on the order of a few tens of microns or less, between the outer edge of the wafer and the outer edge of the ring structure. Such contact or such a small gap, in combination with the flow of purge gas, may prevent diffusion of process gases from the underside of the wafer 3201 through the interface between the wafer 3201 and the ring structure toward the top surface of the wafer 3201. In effect, the ring structure acts to "extend" the outer edge of the wafer to a larger diameter, so that any processing gas that does manage to diffuse beyond the "extended" outer edge contacts the outer edge of the ring structure as opposed to the outer edge of the wafer 3201.

[0173] However, if the ring structure is generally axisymmetric, as shown in Figure 32, the distance between the ring structure and the wafer 3201 will change as the wafer 3201 exhibits bowing. As a result, any gap between the ring structure and the wafer 3201 will be varied around the circumference of the wafer 3201 (or the gap may be made to appear at various points around the wafer). Such a gap may be large enough to allow process gases that are normally prevented from flowing through the wafer / ring structure interface to diffuse through the interface and reach the outer edge of the wafer 3201, thereby contaminating the wafer 3201 / exposing it to undesirable deposition or etching.

[0174] To mitigate or eliminate potential diffusion of process gas through this ring structure / wafer contact surface, the ring structure can have a design that avoids conventional designs in which the surface of the ring structure that contacts or is closest to the wafer is made to be axisymmetric, e.g., planar. Instead, such a surface may be made to have a variable circumferential contour that varies in a manner similar to the variations that may occur in a similar circumferential contour of a wafer (when supported through contact at the wafer edge as shown in FIG. 32).

[0175] "Circumferential contour" means a contour taken along the perimeter of an object. For example, if one takes the surface of a ring structure and intersects it with a cylindrical surface (not an actual object, but a conceptual surface) centered on the central axis of the ring structure, the curve formed by the intersection of the ring structure surface with the cylindrical surface becomes the "circumferential contour" of that ring structure surface. In other words, a circumferential contour is similar to a cross-sectional contour, but is evaluated with respect to the circumference of the cylindrical surface, rather than across a flat surface (as would be the case in a traditional cross-sectional view).

[0176] FIG. 34 shows a top view of the ring structure 3470 resting on the wafer 3401 supported by the wafer support structure 3438 of the shower pedestal 3404. FIG. 35 and FIG. 36 show the circumferential contours of the wafer 3401 and the ring structure 3470 in two different states (in FIG. 35, the ring structure 3470 is lifted off the wafer 3401, and in FIG. 36, the ring structure 3470 rests on the wafer 3401). The circumferential contours in FIG. 35 and FIG. 36 are taken along the dashed-dotted circle of radius R in FIG. 34 and "unfolded" into a flat two-dimensional state for easier visualization. The distance R in this case was chosen to be a value between the inner radius of the ring structure 3470 and the radius of the outer edge of the wafer 3401. More specifically, the distance R in this example was chosen to be the same distance as the distance from the central axis to the contact point between the ring structure 3470 and the wafer 3401.

[0177] 34-36 also show markings for various angular positions around the ring structure. As can be seen in FIG. 35, the circumferential contour of the wafer 3401 shows a periodicity to the circumferential contour that correlates with the angular spacing between the wafer support structures 3438. At each wafer support structure 3438, the circumferential contour of the wafer 3401 is at a maximum height, and halfway between each pair of adjacent support structures, the circumferential contour of the wafer 3401 is at a minimum height. The difference between the maximum and minimum heights is represented in FIG. 35 by the distance β.

[0178] The circumferential contour of the ring structure 3470 is also seen in FIG. 35. The ring structure 3470 has a bottom surface that exhibits a variable circumferential contour that generally matches the circumferential contour of the wafer 3401. For example, if a reference plane is defined to be coincident with the top surface of the ring structure 3470 and perpendicular to the central axis of the ring structure (and / or the central axis of the circumferential contour), the bottom surface of the ring structure may vary such that the perpendicular distance from the reference plane to the bottom surface at a radial distance R from the central axis varies at least between a first value and a second value. The first value and the second value may generally be understood to represent the maximum and minimum distances of the circumferential contour from the reference plane. In general, the transition of the circumferential contour from the first value to the second value (or vice versa) may occur in a smooth manner, e.g., to avoid a stepwise transition, to mimic a gradual change in the amount of wafer deflection that occurs around the wafer.

[0179] In many cases, such variations may be periodic, e.g., repeated in a generally cyclical manner at regular intervals, e.g., every 120°. However, such variations may also be repeating but aperiodic, e.g., at angular positions of 0°, 100°, and 240° around the central axis of the ring structure. In many cases, there are three repeats of each such variation, e.g., to accommodate an area in which a wafer supported at three positions will bend. However, while the examples herein focus on variations having three repeats of such variations to accommodate a wafer supported at three positions along its edge, it will be understood that other embodiments may have more variations to accommodate the circumferential contour of a wafer supported at four or more positions along its edge. For example, in some embodiments, a wafer may be supported at four or more positions along its edge. In some such embodiments, a wafer may be supported at 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 locations along its edge, and the circumferential contour of a ring structure designed for use with a wafer so supported may correspondingly have between 4 and 30 low and high points, e.g., similar to the examples above, as appropriate.

[0180] When the ring structure 3470 is placed over the wafer 3401, the two circumferential contours can be generally aligned and the distance between the ring structure and the wafer along the radius of the circumferential contours can be maintained within a desired threshold, for example, within a distance short enough to prevent potential diffusion of process gases through their contact surfaces.

[0181] In some implementations, the circumferential contour of the ring structure 3470 is defined such that the absolute value of the difference between the first value and the second value is greater than 40 microns and less than or equal to 400 microns, which may potentially enable compensation for wafer edge deflection of between approximately 40 microns and 400 microns. In some such implementations, the absolute value of the difference between the first value and the second value may be greater than or equal to 50 microns and less than or equal to 150 microns, greater than or equal to 100 microns and less than or equal to 200 microns, greater than or equal to 250 microns and less than or equal to 350 microns, or greater than or equal to 300 microns and less than or equal to 400 microns.

[0182] In some cases, the circumferential contour of the ring structure 3470 may be designed such that the absolute value of the difference between the first value and the second value actually exceeds the maximum expected amount of wafer edge deflection in a wafer with which the ring structure 3470 is to be used by a small amount (e.g., on the order of a low tens of microns). For example, the absolute value of the difference between the first value and the second value for the ring structure 3470 may be a third value greater than the maximum expected amount of wafer edge deflection in a wafer with which the ring structure is designed to be used. The third value may be greater than zero microns and less than or equal to 50 microns in some cases, e.g., between zero microns and 40 microns, between zero microns and 30 microns, between zero microns and 20 microns, etc.

[0183] In such an embodiment, the third value may be selected to ensure that there is always contact between the wafer 3401 and the bottom surface of the ring structure 3470 even if there is some variation in the maximum amount of edge bow exhibited by the wafer 3401. For example, the amount of edge bow exhibited by a wafer may vary slightly from wafer to wafer depending, for example, on temperature, the crystal orientation of the wafer, potential local effects due to features patterned on the wafer, thickness variations in the wafer, etc. The maximum amount of wafer bow may be, for example, an average expected maximum amount of wafer bow, beyond which, in some cases, there may be the possibility of additional wafer bow. If the absolute value of the difference between the first and second values ​​for the ring structure 3470 is selected to be greater than the expected amount of wafer edge bow by the third value, this has the effect of placing the ring structure 3470 on the bottom of the wafer edge, i.e., the most bowed part of the wafer edge. At this point, the portion of the ring structure that is disposed on the wafer support structure 3438 may not be in contact with the wafer 3401. However, the weight of the ring structure 3470 presses down on the edge of the wafer 3401, causing the wafer 3401 to bend further until the ring structure rests directly on the portion of the wafer 3401 that is supported by the wafer support structure 3438, thereby allowing the wafer edge to contact the ring structure around its entire periphery. This is shown in Figure 36, where the ring structure 3470 has biased the wafer 3401 by its own weight so as to contact the wafer 3401 along its entire periphery. The circumferential contour of the wafer 3401 prior to such additional deflection is represented in Figure 36 by the dotted outline of the wafer 3401, while the solid outline of the wafer 3401 represents the wafer in its further deflected state.

[0184] FIG. 37 shows a top view of a ring structure 3770 and a wafer 3701 that may be used in some embodiments. FIG. 38 shows a cross-sectional view of FIG. 37, and FIG. 39 shows a detailed view of the circled area in FIG. 38. As can be seen in the detailed view of FIG. 39, the ring structure 3770 overlaps the edge of the wafer 3701 by a small amount, but the overlapping area does not actually contact the top surface of the wafer 3701. The ring structure instead has a bottom surface that has a portion 3755 that is at an oblique angle to the central axis 3715 of the ring structure 3704. This oblique appearance to portion 3755 of the bottom surface of the ring structure 3770 extends entirely around the ring structure 3770, which, in conjunction with the circumferential variations discussed above, may create an undulating frustoconical surface. This surface can rest on the outer edge of the wafer 3701 by being inclined at an oblique angle from the central axis 3715 (as opposed to being perpendicular to the central axis 3715), thereby providing edge contact on the outermost edge of the wafer bevel (as opposed to contacting the top surface of the wafer 3701).

[0185] The ring structures discussed herein may be made from a variety of materials, which may be selected to be resistant or non-reactive to processing chemicals that may be provided to the underside of a wafer being processed. For example, such ring structures may be made from a ceramic material, such as alumina (aluminum oxide), and then machined or polished to obtain a desired circumferentially varying profile.

[0186] The top surface of such a ring structure may in some cases be planar or axisymmetric, as shown in Figures 40 and 41 (top and bottom dual axis views, respectively), allowing the ring structures to be nominally parallel to the underside of a showerhead that may be positioned directly above them, and allowing a constant gap distance to be maintained between the showerhead and the ring structure. In other cases, as shown in Figures 42 and 43, the top surface of the ring structure may also be formed to have a variable circumferential contour, for example, a circumferential contour that generally follows the circumferential contour of the bottom surface of the ring structure. In Figures 42 and 43 (top and bottom dual axis views, respectively), the dashed and dotted lines represent the outer edge of the top surface as if the top surface were planar, for example, as shown in Figures 40 and 41. In actual practice, such a non-axisymmetric top surface typically varies only on the order of tens to hundreds of microns, so that the overall change in height of the top surface is perhaps on the order of a millimeter or less, which can still provide adequate gap control between the showerhead and the ring structure (because purge gas is provided into the gap between the showerhead and the ring structure, gas flow uniformity is not as important as if the process gas were to flow out of the showerhead. The main concern would be to maintain a sufficiently small gap, e.g., on the order of a few millimeters, to avoid potential plasma generation in the gap).

[0187] 44 and 45 show exploded and non-exploded side views of a wafer 4401 resting on the wafer supports 4438 of the shower pedestal 4404 and with a ring structure 4470 installed thereon. As can be seen, the ring structure 4470 aligns with the wafer's deflection area (again, the deflection is exaggerated) to avoid creating a gap (or a larger gap) at the wafer's deflection area.

[0188] In some implementations, the ring structure may have a plurality of protrusions, e.g., a circular array of protrusions, on its bottom surface, which may be positioned to lie along a shaped or non-axisymmetric portion of the bottom surface. FIG. 46 shows an isometric bottom view of an exemplary ring structure 4670 having six protrusions 4673 disposed on the bottom surface of the ring structure 4670 between an inner edge 4672 and an outer edge 4674 of the ring structure 4670. The protrusions 4673 may be positioned at equally spaced locations around the circumference of the ring structure 4670. The protrusions 4673 may be used as minimum contact area (MCA) features that may contact the edge of the wafer with minimal (or practically minimal) surface area contact. For example, the protrusions may be semi-cylindrical ridges that extend along the bottom surface along an axis that is coplanar with a plane that is coplanar with the central axis of the ring structure, e.g., radiating generally outward (and along the bottom surface). This is shown more clearly in FIG. 47, which shows a detailed view of a portion of the ring structure 4670. In the example shown, the protrusion 4673 is located on a generally conical portion of the bottom surface of the ring structure (although this surface may not be truly conical as discussed above. This surface may be shaped to have a periodically varying circumferential contour as in the example above). Thus, when the ring structure 4670 is placed on a wafer such that it contacts the edge of the wafer with its bottom surface, contact between the wafer and the ring structure 4670 may be limited to the protrusion 4673. This may reduce the contact area between the wafer and the ring structure 4675, thereby reducing the possibility of particle generation due to wear between the wafer and the ring structure 4670.

[0189] In some additional or alternative embodiments, a ring structure such as the ring structure described above, or the focus ring previously discussed, may be provided as a multi-piece assembly. For example, the ring structure may have an inner portion and an outer portion surrounding the inner portion. The outer portion may be configured such that the inner portion may rest on and be supported by the outer portion, but may also be lifted vertically upward from the inner portion when subjected to a force from below. Such an embodiment may allow the weight of the ring structure to be shared between its inner and outer portions. Then, when the ring structure contacts a wafer positioned below it, the wafer lifts the inner portion away from the outer portion and supports it. Thus, the wafer may support the weight of the inner portion, but need not support the weight of the outer portion.

[0190] Figure 48 shows an isometric cross-sectional view of an example showerhead 4828 and shower pedestal 4804 supporting a wafer 4801. Figures 49 through 51 show detailed views of the circled portion of Figure 48 through various positions of focus ring 4870, e.g., the ring structure.

[0191] 49, focus ring 4870 has an inner portion 4870a and an outer portion 4870b. Inner portion 4870a may have an inner edge having a diameter smaller than the outer diameter of wafer 4801 and an outer edge having a diameter larger than the inner diameter of outer portion 4870b. For example, outer portion 4870b may have a stepped down region along its inner edge that may act to receive the outer edge of inner portion 4870a. The outer edge of outer portion 4870b may have a diameter larger than the diameter of the inner edge of ring support collar 4871, thereby allowing outer portion 4870b to rest on and be supported by ring support collar 4871.

[0192] In FIG. 49, the focus ring 4870 is supported entirely by the ring support collar 4871 as the showerhead 4828 is elevated relative to the shower pedestal 4804.

[0193] 50, the showerhead 4828 and shower pedestal 4804 have been moved to a relative position where the focus ring 4870 just contacts the wafer support structure 4838 and / or rests on the outer edge of the wafer 4801. In this position, the inner portion 4870a may also still be partially supported by the outer portion 4870b.

[0194] 51 , showerhead 4828 and shower pedestal 4804 have been moved to a relative position where inner portion 4870a of focus ring 4870 rests on the outer edge of wafer support structure 4838 and / or wafer 4801, and outer portion 4870b of focus ring 4870 rests on ring support collar 4871, resulting in a small vertical gap between inner portion 4870a and outer portion 4870b. It will be appreciated that the gap may be smaller than shown, such as such that it is difficult for gases to flow through the interface between inner portion 4870a and outer portion 4870b.

[0195] Such an arrangement allows the size of focus ring 4870 to be increased beyond the size of inner portion 4870a without increasing the weight that focus ring 4870 places on wafer 4801. This allows the weight of focus ring 4870 placed on wafer 4801 to be decoupled, at least to some extent, from the size of focus ring 4870 and the size of showerhead 4828 that can support focus ring 4870.

[0196] FIGS. 52 through 55 show various views of focus ring 4870. FIG. 52 is an isometric view of focus ring 4870 with inner portion 4870a resting on and supported by outer portion 4870b. FIG. 53 is an isometric view of focus ring 4870 with inner portion 4870a lifted away from outer portion 4870b. FIG. 54 is a cross-sectional view of focus ring 4870, and FIG. 55 is a detailed view of the circled portion of FIG. 54. As seen in FIG. 55, inner portion #XR70a of focus ring 4870 includes a pocket or recess 4867 that can engage with a wafer support structure of a shower pedestal, for example, as discussed above with respect to FIG. 10. The inner and outer portions 4870a, 4870b may in most cases be generally axisymmetric (apart from features such as pockets or recesses 4867 or protrusions 4873, if present).

[0197] It will be appreciated that the circumferentially varying ring structures discussed herein may be used in any semiconductor processing system in which the wafer is generally unsupported at its center, but rather supported at discrete points along its edge, resulting in wafer edge deflection, and such structures are not limited to use with the particular system illustrated herein.

[0198] In addition to the control of the wafer backside processing system, control of other equipment (such as wafer handling robots, indexers, etc.) described above may be facilitated, for example, through the use of a controller that may be included as part of the semiconductor processing tool, including the exemplary semiconductor processing tools and / or chambers described above. The above-mentioned systems may be integrated with electronics for controlling their operation before, during, and after processing of the semiconductor wafer or substrate. The electronics may be referred to as a "controller," which may control various components or subparts of the system. Depending on the processing requirements and / or type of system, the controller may be programmed to control any of the processes disclosed herein, including delivery of process gases, temperature settings (e.g., heating and / or cooling), valve operation, light source control for radiant heating, pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operational settings, moving wafers in and out of tools or chambers and other transfer tools and / or load locks connected or interfaced to a particular system. More specifically, such a controller may be configured to control, among other systems, various actuators and motors of the backside wafer processing system.

[0199] Broadly speaking, the controller may be defined as an electronic device having various integrated circuits, logic, storage, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, and the like. Integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files) that determine operational parameters for performing specific processes on or for a semiconductor wafer or for a system. The operational parameters may, in some embodiments, be part of a recipe defined by a process engineer to accomplish one or more process steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon oxides, surfaces, circuits, and / or dies of a wafer.

[0200] The controllers, in some embodiments, may be part of or coupled to a computer, which may be integrated into, coupled to, or otherwise networked to the system, or a combination thereof. For example, the controllers may be in the "cloud" or may be all or part of a fab host computer system, which may enable remote access of wafer processing. The computer may enable remote access to the system to monitor the current progress of a fabrication operation, to examine the history of past fabrication operations, to examine trends or performance metrics from multiple fabrication operations, to change parameters of a current process, to set processing steps to follow a current process, or to start a new process. In some examples, a remote computer (e.g., a server) may provide process recipes to the system over a network, which may include a local network or the Internet. The remote computer may include a user interface that allows for entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controllers receive instructions in the form of data that specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of processing to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, such as by having one or more separate controllers, which are networked together to address a common purpose, such as the processing and control described herein. An example of a distributed controller for such a purpose is one or more integrated circuits on the chamber that communicate with one or more remotely located (e.g., located at platform level or located as part of a remote computer) integrated circuits that combine to control processing on the chamber.

[0201] Without being limited thereto, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0202] As described above, depending on the processing steps to be performed by the tool, the controller may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools located throughout the factory, a main computer, another controller, or tools used in material transport to carry containers of wafers to and from tool locations and / or load ports within a semiconductor manufacturing factory.

[0203] As mentioned above, the apparatus and systems discussed herein can be used to perform processing on at least the underside of a wafer. Such processing can be particularly useful in the context of wafers having multiple feature layers, such as 3D memory structures or logic devices. Such wafers can warp or bend due to the number of feature layers present, due to compressive or tensile forces that may occur within each such feature layer. A system capable of performing processing operations on the underside of such wafers, i.e., on the side of the wafer opposite to the side on which such feature layers reside, may be capable of applying a material film to such wafers that can generate opposing tensile or compressive forces, which can counteract or mitigate stress imbalances across the thickness of the wafer, thereby reducing the wafer's bending or warping.

[0204] A conventional dual-electrode radio frequency plasma enhanced chemical vapor deposition (PECVD) or etching system has one gas-flowing electrode that is used for radio frequency power in generating the plasma and for grounding. Typically, the gas-flowing electrode (also called a showerhead) is on the top surface of the reactor and directs reactants to flow onto the top surface of the wafer, thereby processing only the top surface of the wafer.

[0205] In the system discussed herein, dual gas flow electrodes are provided, one as a shower head and the other as a shower pedestal. Either of the electrodes can function as an RF electrode to provide AC power to enable the use of plasma in film deposition or etching processes. This dual gas flow electrode system can selectively deposit or etch films on both sides or only one side of the wafer.

[0206] In one embodiment, the backside gas flow provided by the shower pedestal allows wafer processing operations to occur on the backside of the wafer, while the frontside gas flow from the showerhead can deposit on the frontside of the wafer. In other embodiments (in separate tools, or even in the same tool, or even at the same station within the same tool), the system can be set up to selectively process only one side of the wafer by switching on and off reactants that cause processing to occur on a particular side of the wafer and replacing them with non-reactive gases (e.g., inert gases).

[0207] The shower pedestal and / or showerhead discussed herein, in some embodiments, may include an active heater that brings process gases flowed therethrough to a desired temperature prior to delivery into a chamber housing the shower pedestal and / or showerhead.

[0208] Broadly speaking, when used for deposition-based processing, the use of a shower pedestal can provide some advantages to combat stress and bowing issues by depositing a film on the backside of the wafer. The backside film can counteract the stress caused by the frontside deposition, thereby creating a neutral stress state (or substantially neutral stress, e.g., stress less than about + / - 150 MPa), resulting in a wafer that exhibits no bowing (or substantially no bowing, e.g., bowing less than about 150 μm). If the film deposited on the frontside is a tensile film, the backside film should also be tensile to balance the overall stress. Similarly, if the frontside film is compressive, the backside film should also be compressive. The backside film can be deposited through a variety of reaction mechanisms (e.g., chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), low pressure chemical vapor deposition (LPCVD), etc.), and thus the equipment discussed herein may generally be useful or adaptable to perform any such type of processing. In some embodiments, plasma enhanced chemical vapor deposition may be used due to the high deposition rates achieved in this type of reaction.

[0209] For a deposition operation, certain deposition parameters can be tailored to create a backside film with a desired stress level. One of those deposition parameters is the thickness of the backside film deposited. Thicker films can induce more stress in the wafer, while thinner films (of the same composition and deposited under the same conditions) can induce less stress in the wafer. Thus, to minimize the amount of material consumed in forming the backside layer, the layer can be deposited relatively thin under conditions that promote the formation of a highly stressed film.

[0210] As mentioned, stacks of materials deposited on the front side of a wafer, for example to create memory or logic circuits, are prone to causing wafer stress and bowing. One exemplary stack that can cause these problems is a stack having alternating layers of oxide and nitride (e.g., silicon oxide / silicon nitride / silicon oxide / silicon nitride, etc.). Another exemplary stack that can cause bowing includes alternating layers of oxide and polysilicon (e.g., silicon oxide / polysilicon / silicon oxide / polysilicon, etc.). Other examples of stack materials that can be problematic include, but are not limited to, tungsten and titanium nitride. The materials in the stack can be deposited through chemical vapor deposition techniques such as plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), metal organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), or direct metal deposition (DMD), etc. These examples are not intended to be limiting. Certain disclosed embodiments can be useful whenever wafer stress and / or bowing is induced due to materials present on the front side of the wafer.

[0211] The front side stack can be deposited to any number of layers and thickness. In a typical example, such a stack may include between about 32 and 72 layers and have a total thickness between about 2 μm and 4 μm. The stress induced in the wafer by the stack can be between about -500 MPa and about +500 MPa, frequently resulting in a bow between about 200 μm and 400 μm (for a 300 mm wafer), and in some cases even larger.

[0212] The material deposited on the backside of the wafer can be a dielectric material in various embodiments. In some cases, oxides and / or nitrides (e.g., silicon oxide / silicon nitride) can be used. Examples of silicon-containing reactants that can be used to create such layers include, but are not limited to, silanes, halosilanes, and aminosilanes. Silanes contain hydrogen and / or carbon groups, but do not contain halogens. Examples of silanes are silane (SiH4), disilane (Si2H6), and organosilanes such as methylsilane, ethylsilane, isopropylsilane, t-butylsilane, dimethylsilane, diethylsilane, di-t-butylsilane, allylsilane, sec-butylsilane, thexylsilane, isoamylsilane, t-butyldisilane, di-t-butyldisilane, and the like. Halosilanes contain at least one halogen group and may or may not contain hydrogen and / or carbon groups. Examples of halosilanes are iodosilanes, bromosilanes, chlorosilanes, and fluorosilanes. Halosilanes, particularly fluorosilanes, can form reactive halide species capable of etching silicon materials, but in certain embodiments described herein, no silicon-containing reactants are present when the plasma is generated. Particular chlorosilanes are tetrachlorosilane (SiCl4), trichlorosilane (HSiCl3), dichlorosilane (H2SiCl2), monochlorosilane (ClSiH3), chloroallylsilane, chloromethylsilane, dichloromethylsilane, chlorodimethylsilane, chloroethylsilane, t-butylchlorosilane, di-t-butylchlorosilane, chloroisopropylsilane, chloro-sec-butylsilane, t-butyldimethylchlorosilane, thexyldimethylchlorosilane, and the like. Aminosilanes contain at least one nitrogen atom bonded to a silicon atom, but may also contain hydrogen, oxygen, halogens, and carbon.Examples of aminosilanes are mono-, di-, tri-, and tetraaminosilanes (H3Si(NH2)4, H2Si(NH2)2, HSi(NH2)3, and Si(NH2)4, respectively), as well as substituted mono-, di-, tri-, and tetraaminosilanes, such as t-butylaminosilane, methylaminosilane, tert-butylsilane amine, bis(tert-butylamino)silane (SiH2(NHC(CH3)3)2 (BTBAS), tert-butylsilylcarbamate, and tert-butylsilylcarbamate. Examples of aminosilanes include silanes such as SiH(CH3)-(N(CH3)2)2, SiHCl-(N(CH3)2)2, (Si(CH3)2NH)3, etc. A further example of an aminosilane is trisilylamine (N(SiH3)). Other promising silicon-containing reactants are tetraethylorthosilicate (TEOS), as well as tetramethoxysilane (TMOS), fluorotriethoxysilane (FTES), trimethylsilane (TMS), octamethyltetracyclosiloxane (OMCTS), tetramethylcyclotetrasiloxane (TMCTSO), dimethyldimethoxysilane (DM ... Silane (DMDS), hexamethyldisilazane (HMDS), hexamethyldisiloxane (HMDSO), hexamethylcyclotrisiloxane (HMCTSO), dimethyldiethoxysilane (DMDEOS), methyltrimethoxysilane (MTMOS), tetramethyldisiloxane (TMDSO), divinyltetramethyldisiloxane (VSI2), methyltriethoxysilane (MTEOS), dimethyltetramethoxydisiloxane (DMTMODSO), ethyltriethoxysilane (ETEOS), ethyltrimethoxysilane (ETMOS), hexamethyldisiloxane (DMDSO), These include cyclic and acyclic TEOS variants such as dimethylethoxydisilane (HMODS), bis(triethoxysilyl)ethane (BTEOSE), bis(trimethoxysilyl)ethane (BTMOSE), dimethylethoxysilane (DMEOS), tetraethoxydimethyldisiloxane (TEODMDSO), tetrakis(trimethylsiloxy)silane (TTMSOS), tetramethyldiethoxydisiloxane (TMDEODSO), triethoxysilane (TIEOS), trimethoxysilane (TIMEOS), or tetrapropoxysilane (TPOS).

[0213] Exemplary nitrogen-containing reactants that can be used to create such layers include, but are not limited to, amines (e.g., amines having carbon) such as ammonia, hydrazine, methylamine, dimethylamine, ethylamine, isopropylamine, t-butylamine, di-t-butylamine, cyclopropylamine, sec-butylamine, cyclobutylamine, isoamylamine, 2-methylbutan-2-amine, trimethylamine, diisopropylamine, diethylisopropylamine, di-t-butylhydrazine, and aromatic compounds containing amines such as aniline, pyridine, and benzylamine. The amines may be primary, secondary, tertiary, or quaternary (e.g., tetraalkylammonium compounds). The nitrogen-containing reactants can contain heteroatoms other than nitrogen, for example, hydroxylamine, t-butyloxycarbonylamine, and Nt-butylhydroxylamine are nitrogen-containing reactants.

[0214] Examples of oxygen-containing co-reactants that may be used to create such layers may include oxygen, ozone, nitrous oxide, carbon monoxide, nitric oxide, nitrogen dioxide, sulfur oxides, sulfur dioxide, oxygen-containing hydrocarbons (CxHyOz), water, mixtures thereof, and the like.

[0215] The flow rates of these reactants may be highly dependent on the type of reaction depositing the backside layer. If CVD / PECVD may be used to deposit the backside layer, the flow rate of the silicon-containing reactant may be between about 0.5 mL / min and 10 mL / min (before atomization), for example, between about 0.5 mL / min and 5 mL / min. The flow rate of the nitrogen-containing reactant, oxygen-containing reactant, or other co-reactant may be between about 3 SLM and 25 SLM, for example, between about 3 SLM and 10 SLM.

[0216] In certain embodiments, the backside layer may be removed after further processing. In that case, the composition of the backside layer may be selected so that the backside layer may be easily removed from the substrate at the appropriate time. In this regard, there may be high selectivity between the material of the backside layer (e.g., dielectric) and the material of the underlying substrate (e.g., silicon) in the desired removal chemistry.

[0217] The optimal thickness of the back layer may depend on the conditions when the back layer is deposited, as well as the magnitude of stress induced by the deposition on the surface of the wafer. The back layer may be deposited to a thickness that results in negligible stress in the wafer (e.g., less than about 150 MPa). In these or other embodiments, the back layer may be deposited to a thickness that results in negligible wafer bow (e.g., less than about 150 μm bow). In some cases, this corresponds to a back layer thickness of between about 0.1 μm and 2 μm, such as between about 0.3 μm and 2 μm, or between about 0.1 μm and 1 μm, or between about 0.3 μm and 1 μm. When silicon nitride is used to form the back layer, a film having a thickness of about 0.3 μm may be sufficient to mitigate bowing of about 50 μm to 200 μm. As mentioned above, a back layer of higher stress may be used to reduce the required thickness of the back layer that is needed to overcome a thicker but lower stress surface layer. This may help to conserve material and reduce costs, for example by requiring less processing time. For more information regarding backside deposition techniques, reference may be made to US Pat. No. 9,881,788, which is owned by the same assignee as the present application and is hereby incorporated by reference in its entirety.

[0218] In this disclosure and claims, the use of ordinal markers, e.g., (a), (b), (c)..., or (1), (2), (3)..., etc., should be understood as not conveying any particular order or sequence, unless such order or sequence, if any, is expressly indicated. For example, where there are three steps labeled (i), (ii), and (iii), it should be understood that those steps may be performed in any order (and even simultaneously, unless otherwise contraindicated) unless otherwise indicated. For example, if step (ii) involves handling an element created in step (i), step (ii) may be considered to occur at some point after step (i). Similarly, if step (i) involves handling an element created in step (ii), the reverse should be understood. It will also be understood that use of the ordinal marker "first" herein, e.g., "first item," should not be construed as implicitly or inherently suggesting that a "second" instance, e.g., "second item," is necessarily present.

[0219] It should be understood that phrases such as "for each <item> of one or more <items>," "for each <item> of one or more <items>," etc., as used herein, are inclusive of both single and multiple items, i.e., the phrase "for each ..." is used in the sense in which the phrase is used in programming languages ​​to refer to each item, whatever the number of individuals of the item being referenced. For example, if the collection of items being referenced is a single item, then "each" refers only to that single item (even though dictionary definitions of "each" often define the word to mean "each of two or more things") and does not mean that there must be at least two of the items. Similarly, it will be understood that the terms "set" or "subset" should not be considered inherently to necessarily include a plurality of items, and that a set or subset may include only one member or multiple members (unless the context indicates otherwise).

[0220] In this disclosure, the term "fluidically connected" is used for volumes, plenums, holes, etc. that may be connected to one another directly or through one or more intervening components or volumes to form a fluid connection, similar to the way the term "electrically connected" is used for components that are connected together to form an electrical connection. The term "fluidically interposed", when used, may be used to mean a component, volume, plenum, or hole that is fluidly connected to at least two other components, volumes, plenums, or holes such that fluid flowing from one of the at least two other components, volumes, plenums, or holes to another or another of those components, volumes, plenums, or holes first flows through the "fluidically interposed" component before reaching the other or another of those components, volumes, plenums, or holes. For example, if a pump is fluidly interposed between a reservoir and an outlet, fluid flowing from the reservoir to the outlet must first flow through the pump before reaching the outlet. The term "fluidically adjacent," as used, refers to the placement of a fluid element relative to another fluid element such that there are no potential fluidically interposed structures between the two elements that could potentially impede fluid flow between the two fluid elements. For example, in a flow path having a first valve, a second valve, and a third valve located successively therealong, the first valve would be fluidly adjacent to the second valve, the second valve would be fluidly adjacent to both the first valve and the third valve, and the third valve would be fluidly adjacent to the second valve.

[0221] The term "between," when used herein in conjunction with a range of values, should be understood to include the beginning and ending values ​​of the range, unless otherwise indicated. For example, between 1 and 5 should be understood to include the numbers 1, 2, 3, 4, and 5, as well as the numbers 2, 3, and 4.

[0222] The term "operably connected" should be understood to mean a state in which two components and / or systems are directly or indirectly connected, for example such that at least one component or system can control the other. For example, a controller may be described as operably connected to a resistive heating unit, including a controller that is connected to a subordinate controller of the resistive heating unit, the subordinate controller being electrically connected to a relay configured to controllably connect or disconnect the resistive heating unit to a power source capable of providing an amount of power that can operate the resistive heating unit to produce a desired degree of heating. It will be understood that the controller itself may not be able to directly provide such power to the resistive heating unit due to the currents involved, but the controller is still operably connected to the resistive heating unit.

[0223] It is understood that the examples and embodiments described herein are merely for illustrative purposes, and various modifications or changes within the scope thereof will be suggested to those skilled in the art. Various details have been omitted for clarity, but various design choices may be implemented. Thus, the examples should be considered as illustrative rather than limiting, and the disclosure is not limited to the details described herein, but may be modified within the scope of the disclosure.

[0224] It should be understood that the above disclosure focuses on certain exemplary embodiments, but is not limited to only the examples discussed, but is equally applicable to similar variations and features, and that such similar variations and features are also considered to be within the scope of the present disclosure. However, the present disclosure is directed to and includes at least the following non-exclusive list of numbered embodiments:

[0225] Embodiment 1: A shower pedestal having a plurality of first gas distribution ports distributed across a first surface thereof, the first surface of the shower pedestal defining a first mean mid-plane; a plurality of wafer support structures extending from the shower pedestal and positioned about a first reference axis, the first reference axis intersecting a first surface of the shower pedestal and perpendicular to a first mean mid-plane; Equipped with A plurality of wafer support structures are further positioned around an area including the first surface of the shower pedestal; each wafer support structure having a corresponding wafer support surface that is non-parallel to the first mean mid-plane; an apparatus, wherein each wafer support surface has a portion positioned at least a first distance from a first mean midplane in a direction perpendicular to the first mean midplane and a second distance from a first reference axis in a direction perpendicular to the first reference axis.

[0226] Embodiment 2: An apparatus as described in embodiment 1, wherein at least a portion of each wafer support surface forms an angle greater than zero degrees and less than or equal to 15 degrees with respect to the first average midplane.

[0227] Embodiment 3: The apparatus of embodiment 1 or 2, wherein each wafer support structure includes a corresponding cantilever structure and a corresponding riser structure, and for each wafer support structure: a corresponding cantilever structure for the wafer support structure extending radially inward from a corresponding riser structure for the wafer support structure toward the first reference axis; a corresponding cantilever structure for the wafer support structure having a proximal end connected to a corresponding riser structure for the wafer support structure; A corresponding cantilever structure for the wafer support structure has a distal end at which a corresponding wafer support surface for the wafer support structure is disposed.

[0228] Embodiment 4: The device according to embodiment 3, each cantilever structure having a corresponding channel on a side of the cantilever structure facing away from the first mean mid-plane; a corresponding channel of each cantilever structure disposed between a wafer support surface of that cantilever structure and a corresponding riser structure connected to a proximal end of that cantilever structure; An apparatus wherein the corresponding channel of each cantilever structure extends across the cantilever structure in a direction transverse to the long axis of the cantilever structure.

[0229] Embodiment 5: A device according to embodiment 4, wherein each channel is at least 0.75 mm deep.

[0230] Embodiment 6: An apparatus described in any one of embodiments 1 to 5, further comprising a plurality of wafer centering features, each wafer centering feature having a corresponding centering surface, at least a portion of the centering surface of each wafer centering feature being positioned at a third distance from the first reference axis and facing the first reference axis.

[0231] Embodiment 7: An apparatus as described in embodiment 6, wherein the third distance is between 150.5 mm and 150 mm.

[0232] Embodiment 8: An apparatus as described in embodiment 6 or embodiment 7, wherein each wafer centering feature is fixed to a corresponding one of the wafer support structures via a gap and supported by the corresponding one of the wafer support structures.

[0233] Embodiment 9: An apparatus as described in embodiment 8, wherein at least a portion of the centering surface of each wafer centering feature forms an angle of less than 90 degrees with respect to the first reference axis.

[0234] Embodiment 10: An apparatus as described in embodiment 8, wherein at least a portion of the centering surface of each wafer centering feature forms an acute angle greater than 0 degrees and less than 30 degrees with the first reference axis.

[0235] Embodiment 11: An apparatus as described in embodiment 6, wherein the wafer centering feature is a wheel.

[0236] Embodiment 12: An apparatus as described in embodiment 11, wherein the wheel is made of a ceramic material.

[0237] Embodiment 13: An apparatus as described in embodiment 11 or embodiment 12, wherein each wheel is supported by a corresponding one of the wafer support structures relative to the shower pedestal and is configured to rotate about an axis at a fixed distance relative to the first mean midplane.

[0238] Embodiment 14: The apparatus of embodiment 13, further comprising a showerhead, the showerhead having a plurality of second gas distribution ports distributed across a second surface of the showerhead facing the first surface of the shower pedestal; There are N wheels, a second surface of the showerhead having N recesses therein; the apparatus wherein each recess is positioned such that a corresponding second reference axis passes through that recess, the second reference axis being perpendicular to the first mean midplane and passing through the center of a corresponding one of the wheels.

[0239] Embodiment 15: The apparatus of embodiment 14, further comprising a focus ring, the focus ring comprising: a nominally circular inner edge having a diameter less than twice the third distance and a nominally circular outer edge having a diameter greater than twice the third distance; and 1. An apparatus configured to rest on a wafer support structure, wherein the focus ring includes N openings proximate an inner edge or N notches along the inner edge, each of the openings or notches positioned such that a portion of a corresponding one of the wheels passes through the opening or notch when the focus ring is supported by the wafer support structure.

[0240] Embodiment 16: The device according to embodiment 15, a focus ring having a top surface and a bottom surface; the focus ring is associated with a central axis and a reference surface perpendicular to the central axis and coincident with the top surface; the bottom surface has a first circumferential contour at a radial distance X from the central axis, the first circumferential contour varying such that a perpendicular distance from a reference plane to the bottom surface at the radial distance X varies periodically between at least a first value and a second value; A device in which 2 times X is greater than the diameter of the nominally circular inner edge and less than the diameter of the nominally circular outer edge.

[0241] Embodiment 17: An apparatus as described in embodiment 16, wherein the focus ring further includes a plurality of protrusions positioned along the bottom surface, each protrusion having a portion located at a radial distance X from the central axis.

[0242] Embodiment 18: An apparatus as described in embodiment 17, wherein each protrusion extends along a corresponding axis that is coplanar with a corresponding reference surface, and the corresponding reference surface is coplanar with the central axis.

[0243] Embodiment 19: A device as described in embodiment 18, wherein each protrusion is semi-cylindrical in shape.

[0244] Embodiment 20: The device according to embodiment 15, a focus ring having an inner portion and an outer portion; an inner edge disposed on the inner portion; the inner portion is dimensioned such that it cannot pass through an opening defined by an innermost edge of the outer portion; A device in which the inner and outer portions are not fixedly connected to one another.

[0245] Embodiment 21: The device according to embodiment 11 or embodiment 12, further comprising one or more wheel vertical lifting mechanisms; Each wheel is supported by a corresponding wheel riser structure; one or more vertical lifting mechanisms configured to generally support the wheel riser structure and be movable between at least a first configuration and a second configuration; at least a portion of each wheel is located farther from the first mean midplane than the wafer support surface in a direction parallel to the first reference axis when the one or more vertical lifting mechanisms are in a first configuration; An apparatus wherein each wheel, when the one or more vertical lifting mechanisms are in the second configuration, is located between the first mean midplane and a location where that wheel was located when the one or more vertical lifting mechanisms were in the first configuration.

[0246] Embodiment 22: The device according to embodiment 21, the one or more vertical lifting mechanisms are further configured to be movable between at least a first configuration, a second configuration, and further a third configuration; The apparatus, wherein the first mean midplane is located between the wafer support surface and at least a portion of each wheel when the one or more vertical lifting mechanisms are in the third configuration.

[0247] Embodiment 23: An apparatus as described in embodiment 21 or embodiment 22, wherein each wheel riser structure passes through a corresponding notch in the outer edge of the shower pedestal or through a corresponding hole passing through the shower pedestal.

[0248] Embodiment 24: An apparatus described in any one of embodiments 21 to 23, wherein each wheel riser structure is positioned at a different angular position around the first reference axis than the wafer support structure.

[0249] Embodiment 25: An apparatus described in any one of embodiments 21 to 23, wherein each wheel riser structure is positioned at the same angular position around the first reference axis as a corresponding one of the wafer support structures.

[0250] Embodiment 26: An apparatus as described in embodiment 25, wherein each wafer support structure has an opening therethrough, and the openings are dimensioned such that a portion of a corresponding one of the wheel riser structures passes through the opening when the one or more vertical lifting mechanisms are moved between the first configuration and the second configuration.

[0251] Embodiment 27: A device according to any one of embodiments 1 to 26, comprising: A chamber; a rotary indexer having a plurality of forks; Further comprising: a rotational indexer configured to rotate the plurality of forks about the first axis of rotation to at least a first rotational position in response to one or more inputs; Each fork has a plurality of wafer lifting surfaces; The apparatus, wherein a first fork of the plurality of forks is positioned such that a wafer lifting surface of the first fork is positioned above the shower pedestal when the plurality of forks is in a first rotational position.

[0252] Embodiment 28: The device according to embodiment 27, the first fork includes two arms, the two arms being located entirely outside a circular region centered on the first reference axis and having a diameter twice the third distance when the plurality of forks are in a first rotational position; The apparatus, wherein each of the arms has one or more protrusions that extend inwardly toward a first reference axis such that when the multiple forks are in a first rotational position, a portion of each protrusion having one of the wafer lifting surfaces lies within a circular region.

[0253] Embodiment 29: An apparatus as described in embodiment 28, wherein each wafer lifting surface is non-parallel to the first average midplane.

[0254] Embodiment 30: An apparatus as described in embodiment 28, wherein at least a portion of each wafer lifting surface forms an angle greater than zero degrees and less than 25 degrees with respect to the first average midplane.

[0255] Embodiment 31: A device according to any one of embodiments 28 to 30, comprising: each of the forks includes a first half and a second half; at least one of the wafer lifting surfaces of each fork is provided by a first half of that fork; at least one other of the wafer lifting surfaces of each fork is provided by a second half of that fork; A first half of the fork is fixed to the first hub via a gap; A second half of the fork is fixed to the second hub via a gap; a first hub connected to a first rotary drive by a first shaft; a second hub connected to a second rotary drive by a second shaft; An apparatus, wherein the first rotational drive and the second rotational drive are configured to be independently actuated for at least a portion of their rotational range of motion.

[0256] Embodiment 32: An apparatus for use with a semiconductor wafer of diameter D, comprising a ring structure having an inner periphery defining an opening dimensioned smaller than the semiconductor wafer of diameter D and an outer periphery dimensioned larger than the semiconductor wafer of diameter D; a ring structure having a top surface and a bottom surface; a ring structure associated with a central axis and a reference surface perpendicular to the central axis and coincident with the top surface; the bottom surface has a first circumferential contour at a radial distance X from the central axis, the first circumferential contour varying such that a perpendicular distance from a reference plane to the bottom surface at the radial distance X varies between at least a first value and a second value; A device wherein X is less than 50% of D.

[0257] Embodiment 33: An apparatus as described in embodiment 32, wherein the vertical distance from the reference plane to the bottom surface at radial distance X changes periodically.

[0258] Embodiment 34: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically around the ring structure with a periodicity of at least 3 periods.

[0259] Embodiment 35: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically with a periodicity of three around the ring structure.

[0260] Embodiment 36: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically with a periodicity of four around the ring structure.

[0261] Embodiment 37: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically around the ring structure with a periodicity of at least 4 periods and not more than 10 periods.

[0262] Embodiment 38: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically around the ring structure with a periodicity of more than 10 periods and less than or equal to 20 periods.

[0263] Embodiment 39: An apparatus as described in embodiment 33, wherein the vertical distance from the reference plane to the bottom surface at radial distance X varies periodically around the ring structure with a periodicity of more than 20 periods and less than or equal to 30 periods.

[0264] Embodiment 40: A device according to any one of embodiments 32 to 39, comprising: there are N spaced first locations about the ring structure, where the first locations have a vertical distance from the reference plane to the bottom surface at a radial distance X at a first value; there are N spaced second locations about the ring structure, where the vertical distance from the reference plane to the bottom surface at the radial distance X is at a second value at the second locations; each first location is circumferentially interspaced between two of the second locations; Each second location is circumferentially interspaced between two of the first locations. A device in which N is an integer greater than or equal to 3.

[0265] Embodiment 41: An apparatus according to embodiment 40, wherein N is 3.

[0266] Embodiment 42: An apparatus according to embodiment 40, wherein N is 4.

[0267] Embodiment 43: An apparatus as described in embodiment 40, wherein N is an integer greater than 3 and less than or equal to 30.

[0268] Embodiment 44: An apparatus as described in embodiment 40, wherein N is an integer greater than 3 and less than or equal to 10.

[0269] Embodiment 45: An apparatus as described in embodiment 40, wherein N is an integer greater than 10 and less than or equal to 20.

[0270] Embodiment 46: An apparatus as described in embodiment 40, wherein N is an integer greater than 20 and less than or equal to 30.

[0271] Embodiment 47: An apparatus described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than zero microns and less than or equal to 400 microns.

[0272] Embodiment 48: An apparatus described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than zero microns and less than or equal to 100 microns.

[0273] Embodiment 49: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 50 microns and less than or equal to 150 microns.

[0274] Embodiment 50: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 100 microns and less than or equal to 200 microns.

[0275] Embodiment 51: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 150 microns and less than or equal to 250 microns.

[0276] Embodiment 52: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 200 microns and less than or equal to 300 microns.

[0277] Embodiment 53: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 250 microns and less than or equal to 350 microns.

[0278] Embodiment 54: A device described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than or equal to 300 microns and less than or equal to 400 microns.

[0279] Embodiment 55: An apparatus described in any one of embodiments 32 to 46, wherein the absolute value of the difference between the first value and the second value is greater than a third value than a predicted maximum amount of wafer edge deflection in a semiconductor wafer when the semiconductor wafer is supported at multiple positions along its edge.

[0280] Embodiment 56: An apparatus as described in embodiment 55, wherein the third value is greater than zero microns and less than 50 microns.

[0281] Embodiment 57: An apparatus as described in embodiment 55, wherein the third value is greater than zero microns and less than or equal to 40 microns.

[0282] Embodiment 58: An apparatus as described in embodiment 55, wherein the third value is greater than zero microns and less than 30 microns.

[0283] Embodiment 59: An apparatus as described in embodiment 55, wherein the third value is greater than 20 microns and less than or equal to 20 microns.

[0284] Embodiment 60: A device described in any one of embodiments 32 to 59, wherein the top surface is planar.

[0285] Embodiment 61: A device described in any one of embodiments 32 to 59, wherein the top surface is axially symmetrical with respect to the central axis.

[0286] Embodiment 62: A device described in any one of embodiments 32 to 61, wherein the top surface has a second circumferential contour that follows the first circumferential contour.

[0287] Embodiment 63: An apparatus described in any one of embodiments 32 to 62, wherein the bottom surface at the radial distance X from the central axis is a wavy truncated cone.

[0288] Embodiment 64: An apparatus described in any one of embodiments 32 to 62, wherein the bottom surface at a radial distance X from the central axis has a radial contour relative to the central axis, the radial contour being at an oblique angle to the central axis.

[0289] Embodiment 65: A device described in any one of embodiments 32 to 64, wherein the ring structure is made from a ceramic material.

[0290] Embodiment 66: An apparatus according to embodiment 65, wherein the ceramic material is aluminum oxide.

Claims

1. An apparatus comprising: a shower pedestal having a plurality of first gas distribution ports distributed across a first surface of the shower pedestal, the first surface of the shower pedestal defining a first mean midplane; a plurality of wafer support structures extending from the shower pedestal and positioned about a first reference axis, the first reference axis intersecting the first surface of the shower pedestal and perpendicular to the first mean mid-plane; the plurality of wafer support structures are further positioned around an area of ​​the shower pedestal that includes the first surface; each wafer support structure having a corresponding wafer support surface that is non-parallel to the first mean mid-plane; each said wafer support surface having a portion positioned at least a first distance from said first mean midplane in a direction perpendicular to said first mean midplane and a second distance from said first reference axis in a direction perpendicular to said first reference axis.

2. 2. The apparatus of claim 1, At least a portion of each of the wafer support surfaces forms an angle with respect to the first mean midplane that is greater than zero degrees and not greater than 15 degrees.

3. 3. The apparatus of claim 2, each said wafer support structure includes a corresponding cantilever structure and a corresponding riser structure, and for each said wafer support structure: the corresponding cantilever structure for the wafer support structure extends radially inward from the corresponding riser structure for that wafer support structure toward the first reference axis; the corresponding cantilever structure for the wafer support structure has a proximal end connected to the corresponding riser structure for the wafer support structure; the corresponding cantilever structure for the wafer support structure has a distal end at which the corresponding wafer support surface for the wafer support structure is disposed.

4. 4. The apparatus of claim 3, each said cantilever structure having a corresponding channel on a side of said cantilever structure facing away from said first mean mid-plane; the corresponding channel of each of the cantilever structures is disposed between the wafer support surface of the cantilever structure and the corresponding riser structure connected to the proximal end of the cantilever structure; wherein the corresponding channel of each of the cantilever structures extends across the cantilever structure in a direction transverse to a longitudinal axis of the cantilever structure.

5. 5. The apparatus of claim 4, Each of said channels is at least 0.75 mm deep.

6. 6. An apparatus according to any one of claims 1 to 5, comprising: the apparatus further comprising a plurality of wafer centering features, each wafer centering feature having a corresponding centering surface, at least a portion of the centering surface of each wafer centering feature positioned a third distance from and facing the first reference axis.

7. 7. The apparatus of claim 6, The apparatus, wherein the third distance is between 150.5 mm and 150 mm.

8. 7. The apparatus of claim 6, an apparatus, wherein each of the wafer centering features is fixed to and supported by a corresponding one of the wafer support structures via a gap therebetween.

9. 9. The apparatus of claim 8, at least a portion of the centering surface of each of the wafer centering features forms an angle of less than 90 degrees with respect to the first reference axis.

10. 9. The apparatus of claim 8, at least a portion of the centering surface of each of the wafer centering features forms an acute angle with the first reference axis that is greater than 0 degrees and less than or equal to 30 degrees.

11. 7. The apparatus of claim 6, The apparatus, wherein the wafer centering feature is a wheel.

12. 12. The apparatus of claim 11, The apparatus wherein the wheel is made of a ceramic material.

13. 12. The apparatus of claim 11, each said wheel is supported by a corresponding one of said wafer support structures relative to said shower pedestal and configured to rotate about an axis that is a fixed distance relative to said first mean midplane.

14. 14. The apparatus of claim 13, a showerhead having a plurality of second gas distribution ports distributed across a second surface of the showerhead facing the first surface of the shower pedestal; There are N said wheels, the second surface of the showerhead has N recesses; each said recess is positioned such that a corresponding second reference axis, perpendicular to said first mean midplane and passing through the center of a corresponding one of said wheels, passes through said recess.

15. 15. The apparatus of claim 14, The focusing ring further comprises: a nominally circular inner edge having a diameter less than twice the third distance and a nominally circular outer edge having a diameter greater than twice the third distance; and 11. An apparatus configured to rest on the wafer support structure, the focus ring including N openings proximate to the inner edge or N notches along the inner edge, the openings or notches positioned such that a portion of the wheel of a corresponding one of the wheels passes through the opening or notch, respectively, when the focus ring is supported by the wafer support structure.

16. 16. The apparatus of claim 15, the focus ring having a top surface and a bottom surface; the focus ring is associated with a central axis and a reference surface perpendicular to the central axis and coincident with the top surface; the bottom surface has a first circumferential contour at a radial distance X from the central axis, the first circumferential contour varying such that a perpendicular distance from the reference plane to the bottom surface at the radial distance X varies periodically between at least a first value and a second value; wherein twice X is greater than the diameter of said nominally circular inner edge and less than the diameter of said nominally circular outer edge.

17. 17. The apparatus of claim 16, the focus ring further includes a plurality of protrusions positioned along the bottom surface, each protrusion having a portion located at the radial distance X from the central axis.

18. 18. The apparatus of claim 17, each said projection extending along a corresponding axis that is coplanar with a corresponding reference surface, said corresponding reference surface being coplanar with said central axis.

19. 20. The apparatus of claim 18, wherein each said protrusion is semi-cylindrical in shape.

20. 16. The apparatus of claim 15, the focus ring having an inner portion and an outer portion; the inner edge is disposed on the inner portion; the inner portion is dimensioned such that it cannot pass through an opening defined by an innermost edge of the outer portion; A device wherein the inner portion and the outer portion are not fixedly connected to one another.

21. 12. The apparatus of claim 11, one or more wheel vertical lift mechanisms; each said wheel being supported by a corresponding wheel riser structure; the one or more vertical lifting mechanisms are configured to generally support the wheel riser structure and be movable between at least a first configuration and a second configuration; at least a portion of each of the wheels is located farther from the first mean midplane than the wafer support surface in a direction parallel to the first reference axis when the one or more vertical lifting mechanisms are in the first configuration; wherein each of the wheels, when the one or more vertical lifting mechanisms are in the second configuration, is located between the first mean mid-plane and a position where that wheel was located when the one or more vertical lifting mechanisms were in the first configuration.

22. 22. The apparatus of claim 21, the one or more vertical lifting mechanisms are further configured to be movable between at least the first configuration, the second configuration, and further a third configuration; the first mean mid-plane is located between the wafer support surface and at least a portion of each wheel when the one or more vertical lifting mechanisms are in the third configuration.

23. 22. The apparatus of claim 21, An apparatus wherein each of the wheel riser structures passes through a corresponding notch in an outer edge of the shower pedestal or through a corresponding hole through the shower pedestal.

24. 22. The apparatus of claim 21, each said wheel riser structure is disposed at a different angular position about said first reference axis than said wafer support structure.

25. 22. The apparatus of claim 21, each said wheel riser structure is disposed at the same angular position about said first reference axis as a corresponding one of said wafer support structures.

26. 26. The apparatus of claim 25, each said wafer support structure having an opening therethrough, the opening being dimensioned such that a portion of the wheel riser structure of a corresponding one of said wheel riser structures passes through the opening when the one or more vertical lift mechanisms is moved between the first configuration and the second configuration.

27. 2. The apparatus of claim 1, A chamber; a rotary indexer having a plurality of forks; Further equipped with the rotational indexer is configured to rotate the plurality of forks about a first axis of rotation to at least a first rotational position in response to one or more inputs; each said fork having a plurality of wafer lifting surfaces; an apparatus wherein a first fork of the plurality of forks is positioned such that the wafer lifting surface of the first fork is positioned above the shower pedestal when the plurality of forks is in the first rotational position.

28. 28. The apparatus of claim 27, the first fork includes two arms, the two arms being located entirely outside a circular area centered on the first reference axis and having a diameter twice the third distance when the plurality of forks are in the first rotational position; each of the arms has one or more protrusions extending inwardly toward the first reference axis such that when the plurality of forks are in the first rotational position, a portion of each protrusion having one of the wafer lifting surfaces lies within the circular area.

29. 29. The apparatus of claim 28, each said wafer lifting surface being non-parallel to said first mean midplane.

30. 29. The apparatus of claim 28, at least a portion of each said wafer lifting surface forms an angle with respect to said first mean midplane that is greater than zero degrees and less than or equal to 25 degrees.

31. 31. Apparatus according to any one of claims 28 to 30, comprising: each of the forks includes a first half and a second half; at least one of the wafer lifting surfaces of each of the forks is provided by the first half of the fork; at least one other of the wafer lifting surfaces of each of the forks is provided by the second half of the fork; The first half of the fork is fixed to a first hub with a gap therebetween; The second half of the fork is fixed to a second hub via a gap; the first hub is connected to a first rotary drive by a first shaft; the second hub is connected to a second rotary drive by a second shaft; An apparatus, wherein the first rotational drive and the second rotational drive are configured to be independently actuated for at least a portion of their rotational range of motion.

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