Pedestal with axisymmetric edge purge plenum

Abstract

The present disclosure relates to a pedestal assembly for supporting a wafer in a semiconductor manufacturing tool and chamber. Such a pedestal assembly may have an edge purge system including an axially symmetric first plenum volume including at least a first radial sub-volume, a first axial sub-volume, and a second radial sub-volume. The first axial sub-volume may be fluidly disposed between the first radial sub-volume and the second radial sub-volume. An optional second plenum volume may be provided and may be used to fluidly connect a region of a wafer support that is part of the pedestal assembly with a vacuum port so that the wafer support can provide a vacuum clamping function.

Description

[Background technology]

[0001] [Related Applications] PCT applications are filed concurrently herewith as part of this application. Each application to which this application claims the benefit of or priority to a concurrently filed PCT application is hereby incorporated by reference in its entirety for all purposes.

[0002] Semiconductor processing tools typically require the delivery of different reactive gases to a wafer processing space located within one or more semiconductor processing chambers. The semiconductor wafers processed within such chambers are typically supported on a pedestal (e.g., a platform that may have a chuck or other system for securing the wafer in place on a wafer support surface) during processing operations.

[0003] Described herein are various improvements to pedestals for use in several semiconductor processing systems. 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 detailed description below. Other features, aspects, and advantages will become apparent from the detailed description, the drawings, and the claims.

[0005] In some embodiments, an apparatus may be provided that includes a pedestal assembly. The pedestal assembly may include a wafer support having a bottom surface and an inverted top surface, the wafer support configured to support a wafer of diameter D such that the wafer is centered on a central axis of the pedestal assembly during semiconductor processing operations. The pedestal assembly may have a first plenum volume that is substantially axisymmetric about the central axis of the pedestal assembly. The first plenum volume may include a first axial sub-volume, a first radial sub-volume, and a second radial sub-volume. The first axial sub-volume may fluidly connect and be fluidly disposed between the first radial sub-volume and the second radial sub-volume. Both the first radial sub-volume and the second radial sub-volume may extend radially inward from the first axial sub-volume toward the central axis. The first radial sub-volume may extend radially inward to a location outside a cylindrical section of diameter D centered about the central axis. In contrast, the second radial sub-volume may extend radially inward to a position inside a cylindrical region centered on the central axis and having a diameter D. The second radial sub-volume may be farther from the top surface of the wafer support than the first radial sub-volume.

[0006] In some embodiments, the apparatus may further include a purge inlet fluidly connected to a first plenum volume in the base assembly. The first plenum volume may be configured such that when gas is flowed into the base assembly through the purge inlet, the gas flows radially outward relative to the central axis from the second radial sub-volume to the first axial sub-volume and then from the first axial sub-volume to the first radial sub-volume before exiting the base assembly via the first radial sub-volume.

[0007] In some embodiments, the second radial sub-volume may be free from obstructions for a total arc of at least 320° relative to the central axis.

[0008] In some embodiments, the pedestal assembly may further comprise a ring structure having a peripheral wall portion and a flange portion extending radially inward from the peripheral wall portion to a nominally circular opening of a diameter greater than D. The pedestal may comprise a substructure having an annular portion with a top surface facing away from the bottom surface of the wafer support. In such embodiments, a first axial sub-volume may be disposed radially between the peripheral wall portion and the outermost surface of the wafer support, a first radial sub-volume may be disposed between the flange portion and the wafer support, and a second radial sub-volume may be disposed between the substructure and the wafer support.

[0009] In some such embodiments, the base structure may include a plurality of bosses extending from its top surface to contact the bottom surface of the wafer support, hi some further such embodiments, the bosses may occupy a total arc of less than 40° relative to the central axis.

[0010] In some such embodiments, each boss may have a corresponding lift pin hole therethrough and may have a contact surface that contacts the wafer support, and both the contact surface of each boss and the portion of the wafer support that contacts the boss at the contact surface may be flat.

[0011] In some embodiments, the first plenum volume may further include a second axial sub-volume, the second radial sub-volume may be fluidly disposed between the first axial sub-volume and the second axial sub-volume, the substructure may further comprise a tubular portion having an upper end proximate to the annular portion, the tubular portion may support the annular portion, and the second axial sub-volume may be at least partially surrounded by an inner surface of the tubular portion.

[0012] In some embodiments, the apparatus may further include a first compliant seal element and a support collar, the first compliant seal element may be in a load path that includes a tubular portion and spans between the support collar and the annular portion of the substructure, and the first compliant seal element may apply a compressive load to the annular portion of the substructure to press the substructure against the wafer support.

[0013] In some embodiments, the first plenum volume may further include a second axial sub-volume, and the second radial sub-volume may be fluidly disposed between the first axial sub-volume and the second axial sub-volume.

[0014] In some embodiments, the pedestal assembly may further include a second plenum volume, one or more vacuum outlets, and one or more vacuum ports. The second plenum volume may be fluidly isolated from the first plenum volume within the pedestal assembly, the one or more vacuum ports may connect from the bottom side to the top surface of the wafer support, and the second plenum volume may fluidly connect and be fluidly disposed between the one or more vacuum ports and the one or more vacuum outlets.

[0015] In some embodiments, the apparatus may further comprise a tubular element partially enclosing the second plenum volume.

[0016] In some embodiments, the apparatus may further include a stem, which may support the wafer support, the tubular element may surround the stem, and the second plenum volume may be further enclosed at least in part by the stem.

[0017] In some embodiments, the apparatus may further include a first compliant seal element, a second compliant seal element, and a support collar. The first compliant seal element may include a tubular portion and be in a first load path spanning between the support collar and the annular portion of the substructure, and the second compliant seal element may include a tubular portion and be in a second load path also spanning between the support collar and the annular portion of the substructure. The first compliant seal element may apply a compressive load to the annular portion of the substructure to press the substructure against the wafer support, and the second compliant seal element may be positioned to apply a compressive load to the annular portion of the substructure to press the substructure against the wafer support.

[0018] In some embodiments, the ring structure, the substructure, and the wafer support may all be made of ceramic materials.

[0019] In some embodiments, the ring structure may be made of aluminum nitride and the substructure may be made of aluminum oxide.

[0020] In some embodiments, the wafer support may further include a plurality of low contact area (LCA) features distributed across a portion of the top surface of the wafer support, and each LCA feature may be a protrusion from a concave portion of the top surface of the wafer support.

[0021] In some embodiments, the apparatus further comprises a showerhead configured to direct one or more process gases toward the upper surface of the wafer support when the one or more process gases are flowed through the showerhead.

[0022] In some embodiments, the apparatus may further include a semiconductor processing chamber within which the wafer support is located. [Brief explanation of the drawings]

[0023] In the following description, reference is made to the following figures, which are not intended to be limiting in scope and are provided solely to facilitate the following description:

[0024] [Figure 1] FIG. 10 is a cross-sectional side view of an exemplary pedestal assembly embodying an axially symmetric purge gas plenum volume.

[0025] [Figure 2] Same as Figure 1, except most of the callouts have been removed, the structural features are shown in light grey, and the various elements shown in black are the various plenum volumes and subvolumes.

[0026] [Figure 3] Detail of the corresponding area in Figure 1, where the ring structure and adjacent structures are visible.

[0027] [Figure 4] FIG. 2 is a perspective view of an exemplary undercarriage separated;

[0028] [Figure 5] A detailed view of a portion of the support collar in Figure 1. [Figure 6] A detailed view of a portion of the support collar in Figure 1.

[0029] [Figure 7] FIG. 2 is an enlarged view of the exemplary pedestal assembly of FIG. 1.

[0030] [Figure 8] 8 is a cross-sectional view of the pedestal assembly of FIGS. 1-7 in a semiconductor processing chamber.

[0031] [Figure 9] Detail of the circular part of Figure 8.

[0032] The above figures are provided to facilitate understanding of the concepts described in this disclosure and are intended to illustrate, but not limit, some embodiments falling within the scope of this disclosure. Consistent with this disclosure, embodiments not shown in the figures are also considered to be within the scope of this disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0033] As noted above, semiconductor processing tools or chambers typically use a pedestal to support a wafer during processing operations. Such pedestals may incorporate various subsystems to facilitate processing operations. The subsystems may include, for example, an electrode that may be used to generate RF energy to ignite a plasma within the chamber, heater and cooling systems for thermal management of the wafer, a lift pin mechanism for raising and lowering the wafer relative to the pedestal, and / or a chuck system for clamping the wafer in place during processing operations.

[0034] In some cases, reactants involved in a particular processing operation may be flowed into the space between the backside of the wafer being processed and the wafer support surface of the pedestal on which the wafer rests. This can occur even when there is no pressure differential between the chamber interior and the backside of the wafer that draws such gases under the wafer. For example, molecules of such gases may actually diffuse into the space between the wafer and the wafer support surface even when the wafer edge rests on a continuous, uninterrupted portion of the wafer support surface. In systems in which the wafer is clamped to the pedestal using a vacuum chuck, e.g., by drawing a vacuum under the wafer, so that the region between the wafer and the wafer support surface is at a pressure lower than the pressure within the processing chamber, the resulting pressure differential between the backside of the wafer and the chamber atmosphere may actually act to draw process gases under the wafer out of the chamber.

[0035] Process gases reaching the backside of the wafer can cause unwanted deposition or etching on the wafer edge (e.g., the backside of the wafer adjacent the edge) or wafer bevel (the outer edge of a wafer typically has a rounded shape that avoids the presence of hard / sharp edges that are susceptible to damage or cause burrs, and is called the bevel). One technique for preventing or reducing the likelihood of process gases reaching the backside of the wafer or wafer bevel is to provide a purge gas (e.g., nitrogen, helium, argon, etc. (a gas selected to be non-reactive with the process gases used)) around the wafer.

[0036] The inventors have determined that the pedestal assembly described herein can be used to provide uniform edge purging of a wafer around its entire periphery. For example, a pedestal having a ring of purge gas ports surrounding the wafer and directing purge gas toward the wafer can be used. However, because the purge gas is introduced at different locations proximate the wafer, the purge gas will always exhibit different concentrations around the periphery of the wafer, resulting in corresponding local variations in the effectiveness of the purge gas in preventing unwanted exposure of the backside and bevel regions of the wafer to process gas. This results in corresponding peripheral differences in the extent to which the process gas can affect the backside and / or bevel of the wafer.

[0037] To address this issue, the inventors have conceived a pedestal assembly, as described herein, that can deliver purge gas nearly uniformly around the entire circumference of the wafer, avoiding or mitigating potential peripheral variations in the amount of delivered purge gas. Such a pedestal assembly may generally be formed by an axially symmetric first plenum volume having at least a first radial sub-volume, a first axial sub-volume, and a second radial sub-volume. The first axial sub-volume may fluidly connect the first radial sub-volume with the second radial sub-volume. Both the first radial sub-volume and the second radial sub-volume may extend radially inward from the first axial sub-volume, with a portion of the pedestal assembly's wafer support disposed between the first and second radial sub-volumes. Such an arrangement allows the purge gas to flow through the first plenum volume, for example from the second radial subvolume to the first axial subvolume, then from the first axial subvolume to the first radial subvolume, and be directed so as to be evenly distributed over the edge of the wafer.

[0038] The first plenum volume will generally be immune to any radial obstructions (e.g., features that block the flow of gas along a plane parallel to the central axis of the pedestal assembly). However, to the extent such radial obstructions are necessary, their effect can be minimized, for example, by limiting the proximity of such radial obstructions to the first axial subvolume and / or by limiting the total arc angle about the central axis of the pedestal assembly that such obstructions occupy. For example, in some embodiments, three posts or bosses may extend through the second radial subvolume to allow the lift pins of the pedestal assembly to penetrate the wafer support of the pedestal assembly. However, such features may be limited in size or number to reduce or minimize the disruptive effect they have on the gas flowing through the first plenum volume. For example, in some embodiments, such features may occlude an arc of at most 20°, 30°, or 40°.

[0039] By using a first plenum volume that includes radial sub-volumes both above and below the wafer support and connecting the radial sub-volumes (all of which are substantially axially symmetric about the central axis of the pedestal assembly) with the axial sub-volumes, the flow path of the purge gas exiting the pedestal assembly may be maintained axially symmetric for a significant portion of its length (e.g., extending from a portion of the first radial sub-volume closest to the central axis through the first axial sub-volume and at least some, if not all, of the second radial sub-volume). At the point where the purge gas is introduced into the first plenum volume, such a relatively long, axially symmetric flow path will generally result in less circumferential variation in purge gas delivery from the first plenum volume, provided that such a relatively long, axially symmetric flow path allows circumferential variations in the concentration of the purge gas to equalize before exiting the first plenum volume.

[0040] FIG. 1 shows a cross-sectional side view of an exemplary pedestal assembly embodying an axially symmetric purge gas plenum volume. FIG. 2 is the same as FIG. 1, except that most of the callouts have been removed, structural features are shown in light gray, and various elements shown in black are various plenum volumes and subvolumes. As shown in FIG. 1, the pedestal assembly 108 can include various structures that define a substantially axisymmetric first plenum volume 130 within the pedestal assembly. The first plenum volume 130 can include at least a first radial subvolume 136, a first axial subvolume 132, and a second radial subvolume 138. For example, the first radial subvolume 136 can be partially bounded by the top surface 124 of the wafer support 110 (opposite the bottom surface 126 of the wafer support 110) and the underside of a flange portion of a ring structure 144 that surrounds the wafer support 110. For example, a flange portion of the ring structure 144 may be vertically offset from a portion of the wafer support 110 located immediately below it, thereby forming a circumferential vertical gap between the wafer support 110 and the ring structure 144 in which the first radial sub-volume 136 is located. The ring structure 144 may, for example, be nominally circular and have a central opening having a diameter, for example, about one or several millimeters larger than the diameter D of a wafer to be processed using such a pedestal assembly 108.

[0041] Similarly, the second radial sub-volume 138 may be partially enclosed by, for example, the bottom surface 126 of the wafer support 110 and the top surface of the base structure 152. For example, the base structure 152 may be generally vertically offset from the bottom surface 126 of the wafer support 110, thereby forming a vertical gap between the bottom surface 126 and the base structure 152 in which the second radial sub-volume 138 is located.

[0042] The first axial sub-volume 132 may likewise be partially surrounded by an inwardly facing surface of a peripheral wall portion of the ring structure 144 that surrounds the outermost surface of the wafer support 110. The first axial sub-volume 132 may also be partially surrounded by an outwardly facing surface of the wafer support 110. Thus, the first axial sub-volume may be located in a radial gap between the peripheral wall portion of the ring structure 144 and the outer periphery of the wafer support 110.

[0043] The first radial sub-volume 136 may extend radially inward to a point generally located outside the cylindrical region 142, while the second radial sub-volume 138 may extend radially inward to a point generally located inside the cylindrical region 142. In some cases, the second radial sub-volume may have no obstructions between its outermost edge and the cylindrical region. In some such embodiments, the radius of the cylindrical region may be less than 90%, less than 85%, less than 75%, less than 60%, less than 50%, or less than 40% of the distance from the central axis 128 to the outermost portion of the wafer support 110.

[0044] In this example, the wafer support 110 is designed to function as a vacuum chuck. To that end, the wafer support 110 includes vacuum ports 120, low contact area (LCA) features 116, and a seal ring 122. The seal ring 122 is generally an annular raised portion of the top surface 124 of the wafer support 110, machined, polished, lapped, etc., to provide a flat surface that can contact the edge region of a wafer placed thereon to form a generally hermetic seal around the wafer. The LCA features 116 may be, for example, protrusions, ridges, mesas, or bosses in an otherwise concave portion of the top surface 124 of the wafer support 110, and may be generally evenly distributed across the entire top surface 124. The LCA feature 116 has a top surface that is generally flush with the top surface of the seal ring 122, such that the wafer is supported across its entire diameter by the LCA feature 116, and when a vacuum is drawn on the backside of the wafer via the vacuum ports 120, the wafer may be clamped to the seal ring 122 and the LCA feature 116 without significant bowing / cupping. It will be understood that other patterns of LCA feature 116 may be used depending on the needs of a particular processing regime.

[0045] However, in other embodiments, the wafer support 110 can omit the vacuum ports 120, the LCA feature 116, and / or the seal ring 122. For example, the wafer support 110 may have no wafer clamping capability at all, or may include electrostatic clamping functionality that enables the wafer support 110 to be used as an electrostatic chuck (ESC). For example, one or more electrodes may be embedded within the material of the wafer support 110 and may provide a DC potential that electrostatically attracts the wafer to the top surface 124 of the wafer support 110.

[0046] In this example, the substructure 152 includes an annular portion 154 and a tubular portion 158, with the upper end of the tubular portion 158 adjacent to the annular portion 154. The annular portion 154 may generally extend radially outward from the tubular portion 158, e.g., in the form of a large-diameter flange. The annular portion 154 may extend outward to contact and support the lower portion of the ring structure 144. FIG. 3 shows a detailed view of the corresponding area of ​​FIG. 1, where the ring structure 144 and adjacent structures are visible. As shown in FIG. 3, the ring structure 144 has a peripheral wall portion 146 (e.g., a generally short, large-diameter, thick-walled tube) that connects to a flange portion 148 that extends radially inward therefrom. Also visible in the cross section of FIG. 3 (and FIG. 1) is an indexing post or feature 150, which is a cylindrical feature protruding from the underside of the flange portion 148. The indexing posts or features 150 are relatively small, e.g., occupying only one or two degrees of arc around the ring structure 144, and are intended to engage with corresponding radial slots 118 in the wafer support 110. The ring structure 144 can include multiple (e.g., three) indexing posts or features 150 to constrain the position of the ring structure 144 relative to the wafer support 110. For example, the radial slots 118 can be sized slightly larger than the indexing posts or features 150 (except for a slight difference in the width of the radial slots 118 and the size of the indexing posts or features 150 in the same direction) so that the indexing posts or features 150 can move radially within the radial slots 118 but cannot move tangentially. Such an arrangement can be used to guide the ring structure 144 to center about the central axis 128 of the pedestal assembly 108 (and wafer support 110).

[0047] In some embodiments, the indexing posts or features 150 may have a sufficient vertical height (or the radial slots 118 may have a sufficient vertical depth) such that the bottoms of the indexing posts or features 150 contact the bottoms of the radial slots 118, thereby allowing the ring structure 144 to rest on and be supported by the wafer support 110. In other embodiments, as shown in FIG. 3 , the ring structure 144 may not be supported by the wafer support 110, but instead rest directly on the base structure 152. For example, the bottom surface of the peripheral wall portion 146 of the ring structure may be machined, polished, lapped, etc. to form a contact seal with the top surface 156 of the base structure 152, thereby preventing, or at least impeding, the flow of purge gas from the first plenum volume 130 through the interface between the ring structure 144 and the base structure 152.

[0048] In the illustrated example, the vertical position of the ring structure 144 relative to the wafer support 110 (and thereby the flange portion 148 (shown in dotted lines in FIG. 3 ) relative to the wafer 106) is controlled by the vertical positioning of a base structure 152 supporting the ring structure relative to the wafer support 110. A plurality (e.g., three or more) of bosses 160 are provided projecting from an annular portion 154 of the base structure 152 (or projecting downwardly from the bottom surface 126 of the wafer support 110) to provide positive stops that limit upward movement of the base structure 152 relative to the wafer support 110, thereby providing vertical positioning of the base structure 152 relative to the wafer support 110. In the illustrated example, the base structure 152 (or more precisely, the bosses 160, which are part of the base structure 152 in this example) is compressed against the bottom surface 126 of the wafer support 110 by a compressive force provided by a first compliant seal 164 (described below). Such an arrangement may serve to vertically position the ring structure 144 and substructure 152 relative to the wafer support 110, thereby forming the first radial sub-volume 136 and the second radial sub-volume 138, while allowing radial translational movement between these three structures, thereby accommodating potential mismatches in thermal expansion coefficients between the materials used in these structures.

[0049] As mentioned above, features such as bosses 160 may be designed to occupy an arc of less than 20°, 30°, or 40° in some embodiments. FIG. 4 shows a perspective view of an exemplary base structure 152 in isolation. The central axis 128 of the base assembly 108 and the bosses 160 are shown. As shown, each of the three bosses 160 intercepts (or partially intercepts) an angular area spanned by an arc angle of θ1, θ2, or θ3, respectively. In such embodiments, the sum of θ1, θ2, and θ3 would be less than 20°, 30°, or 40° of arc.

[0050] In this example, the boss 160 also serves as a conduit through which a lift pin is inserted to reach the backside of the wafer 106 supported by the wafer support 110. For example, the wafer support 110 may have a lift pin hole 112 with a corresponding lift pin hole 112 passing through the boss 160 and the annular portion 154 of the base structure 152. The lift pin hole 112 may be sized larger than the diameter of the lift pins used in the pedestal assembly, thereby allowing the lift pins to pass through the base structure 152 and the wafer support 110 to reach the wafer 106. In such a case, the top or contact surface of the boss 160 (and any surface of the bottom surface 126 of the wafer support 110 that may contact the boss 160) may be machined flat, polished, lapped, etc. to form a contact seal between the boss 160 and the bottom surface 126 of the wafer support 110, preventing or reducing the possibility of purge gas leaking from the first plenum volume 130 through the lift pin hole 112. Alternatively, in embodiments in which the boss 160 protrudes from the bottom surface 126 of the wafer support 110, the bottom surface of the boss 160 and the top surface 156 of the base structure 152 may be machined, polished, lapped, etc. to form a contact seal.

[0051] In the illustrated example, the first plenum volume 130 also includes a second axial sub-volume 134 that serves to extend the length of the flow path through the first plenum volume 130 beyond that provided by the first radial sub-volume 136, the first axial sub-volume 132, and the second radial sub-volume 138. This provides additional flow path length that can serve to further equalize the circumferential pressure and flow rate of the purge gas as it exits the first plenum volume 130, for example, near the edge of the wafer 106.

[0052] As described above, the base structure 152 in this example is compressed against the bottom surface 126 of the wafer support 110 by a first compliant seal 164. The first compliant seal 164 may be, for example, a metal bellows seal compressed between the base structure 152 (e.g., its tubular portion 158) and a support collar 172. The first compliant seal 164 may function not only as a seal but also as a spring, providing a compressive force or load that may be used to press the base structure 152 against the wafer support 110 (e.g., the annular portion 154). The support collar 172 may function to support the wafer support 110, for example, via a stem 114. The stem 114 may be connected to or be an integral part of the wafer support 110, for example. As shown, the stem 114 is a separate component that is bonded (e.g., by diffusion bonding) to the wafer support 110 and serves to structurally support the wafer support 110. It will be appreciated that the first compliant seal 164 may be configured, more generally, to be in a load path that includes a tubular portion and extends between the support collar 172 and the annular portion 154 of the base structure 152, to apply a compressive load to the annular portion 154 of the base structure 152, urging the base structure 152 against the wafer support 110. The first compliant seal 164 may be positioned, for example, as shown, or alternatively may be positioned between the tubular portion 158 of the base structure 152 and the annular portion 154 of the base structure 152.

[0053] The illustrated base assembly 108 also includes a tubular element 162 radially disposed between the tubular portion 158 of the lower structure 152 and the stem 114. Thus, the second axial subvolume 134 is partially bounded by the inner surface of the tubular portion 158 of the lower structure 152 and the outer surface of the tubular element 162. The tubular element 162 may have an inner surface that partially encloses the second plenum volume 140. The second plenum volume 140 may be partially bounded by the outer surface of the stem 114 and may fluidly connect the vacuum port 120 to one or more vacuum outlets 168 of the support collar 172 (a single vacuum outlet 168 is shown in this example, but more can be used). The tubular element 162 may be positioned to be compressed against the bottom surface 126 of the wafer support 110 by a second compliant seal 166 (which may be similar in nature to the first compliant seal 164) that applies a compressive load to the tubular element 162. It will be appreciated that the first compliant seal 164 and the second compliant seal 166 can be positioned in other locations. For example, the second compliant seal 166 can be selectively positioned between the tubular element 162 and the bottom surface 126 of the wafer support 110. Similarly, if the annular portion 154 and the tubular portion 158 of the substructure 152 are two separate pieces, the first compliant seal 164 can be selectively positioned between the annular portion 154 and the tubular portion 158 (with the tubular portion 158 connected to or an extension of the support collar 172 so as to form a sealed interface). It will be appreciated that the second compliant seal 166 can, more generally, include the tubular element 162 and be in a load path between the support collar 172 and the annular portion 154 of the substructure 152, and can be configured to apply a compressive load to the tubular element 162, pressing the tubular element 162 against the wafer support 110.

[0054] In embodiments of the pedestal assembly in which a vacuum clamping or chuck feature is not used, the vacuum port 120, the vacuum outlet 168, and the tubular element 162 may optionally be omitted. In such embodiments, the second axial sub-volume 134 of the first plenum volume 130, if present, may instead be partially bounded by the inner surface of the tubular portion 158 of the substructure 152 and the outer surface of the stem 114.

[0055] 5 and 6 show detailed views of a portion of the support collar 172. As can be seen in FIGS. 5 and 6, the support collar 172 is constructed in two separate parts, a first part 174 and a second part 176, which are held together by a first fastener 188 to allow for machining of various internal cavity features of the support collar 172. In such a multi-part construction, the support collar may include one or more first O-ring seals 182 that may be used to seal between such parts, for example, where a pressure differential may exist between the vacuum environment of the second plenum volume 140 and the purge gas environment of the first plenum volume 130.

[0056] The illustrated support collar 172 includes an annular plenum 194 fluidly connected to a plurality of angled passages 196, which are in turn fluidly connected to the first plenum volume 130. Both the annular plenum 194 and the angled passages 196 would be difficult or impossible to machine if the illustrated support collar 172 were machined as a single piece, but would be relatively easy to machine in a multi-piece assembly. However, the support collar 172 may also be a one-piece part, for example, a cast part (e.g., using investment casting) or an additively manufactured part (e.g., using direct metal laser sintering). In that case, such internal features can still be used without requiring a multi-piece approach. In other embodiments, the features used to fluidly connect the first plenum volume 130 with a purge gas source and, if present, the second plenum volume 140 with a vacuum pump or source may be implemented differently than in the illustrated support collar 172.

[0057] In the illustrated support collar 172, the vacuum outlet 168 is a straight, vertical hole that penetrates the support collar 172 and fluidly connects to the second plenum volume 140. As can be seen in FIG. 5 , the vacuum outlet 168 exits the top end of the support collar 172, where it is covered by a clamp 190 that is compressed to the support collar 172 by the second fastener 186. The clamp 190 that can be used to clamp the stem 114 to the support collar 172 is actually a multi-piece clamp (e.g., two C-shaped pieces) with an annular recess on its underside. The annular recess allows gas flow (shown by the gray arrow) from the second plenum volume 140 to the vacuum outlet 168. The clamp 190 can be clamped to the support collar 172, for example, by applying a compressive load to a shoulder 192 of the stem 114. If desired, one or more second O-rings 184 may be disposed between the stem 114 and the support collar 172 to provide an airtight seal between the second plenum volume 140 and the interior of the stem 114.

[0058] 6, the support collar 172 may include one or more purge inlets 170. Each purge inlet 170 may provide a fluid connection between a purge gas source (e.g., a gas line leading to an appliance that supplies the purge gas) and features within the support collar 172 (e.g., the annular plenum 194 and the angled pathway 196) that may be used to flow purge gas (shown by the white arrows) into the first plenum volume 130 and then to the wafer edge.

[0059] FIG. 7 shows the example pedestal assembly of FIG. 1 in an exploded view. Here, the radial slot 118, as well as the LCA feature 116, vacuum port 120, lift pin hole 112, and clamp 190, can be more clearly seen. During assembly, the second O-ring 184 can be installed in the circular groove in the first portion 174 of the support collar 172. The stem 114 can then be inserted into the first portion 174 of the support collar 172 so that the shoulder 192 of the stem 114 contacts the second O-ring 184. The clamp 190 can then be installed around the stem 114 so that it contacts both the shoulder 192 of the stem 114 and the first portion 174 of the support collar 172. The second fastener 186 can then be inserted into the hole in the clamp 190 and threaded through a corresponding threaded hole in the first portion 174 of the support collar 172. At this point, the first portion 174 of the support collar may be fixedly connected to the stem 114. The stem 114 may be connected to the wafer support 110 if it is not already connected to the wafer support 110.

[0060] Alternatively, second portion 176 of support collar 172 may be formed by mounting first compliant seal 164 and second compliant seal 166 in corresponding circular seats or grooves in second portion 176. Tubular element 162 may then be placed in the same groove or seat that houses second compliant seal 166 so as to rest on top of second compliant seal 166, and tubular portion 158 of substructure 152 may likewise be placed in the same groove or seat that houses first compliant seal 164 so as to rest on top of first compliant seal 164.

[0061] The first portion 174 of the support collar 172, along with the attached stem 114 and wafer support 110, may then be inserted through the tubular element 162 and into the second portion 176 of the support collar 172 until the first portion 174 abuts the second portion 176, and the tubular element 162 and substructure 152 are compressed against the bottom surface 126 of the wafer support 110 by compression of the first compliant seal 164 and the second compliant seal 166. At this point, a first fastener 188 may be inserted through the hole in the second portion 176 and into a corresponding threaded hole in the first portion 174, thereby securing the first and second portions 174 and 176 together to form the assembled support collar 172. The ring structure 144 may then be installed on the wafer support 110 so that it rests on the substructure 152. Of course, during such assembly, the index features (eg, posts) 150 may be aligned with the radial slots 118 and the lift pin holes 112 in the wafer support 110 may be aligned with corresponding lift pin holes 112 in the base structure 152 .

[0062] It will, of course, be understood that the above assembly process may be modified as needed depending on the particular design of the components being used. For example, if an integral support collar 172 is used, the clamp 190 may have a threaded stud that passes through the support collar 172, such that a nut would be inserted onto the exposed end of the stud to allow tightening of the clamp 190 even when access to the clamp 190 is obstructed by the presence of the tubular element 162 and / or substructure 152.

[0063] Figure 8 shows a cross-sectional view of the pedestal assembly of Figures 1-7 for a semiconductor processing chamber. Figure 9 shows a detailed view of the circular portion of Figure 8.

[0064] As shown in Figures 8 and 9, the exemplary pedestal assembly 108 described herein may be housed (at least partially) within a chamber 102 that is part of a semiconductor processing tool (e.g., a system that houses multiple processing chambers or a system having processing chambers that can simultaneously house multiple wafers for processing operations).

[0065] The chamber 102 may at least partially house a showerhead 104. The showerhead 104 may be centered above a pedestal assembly 108 and may have a plurality of gas distribution ports distributed across its lower surface (e.g., similar to the LCA features 116 distributed across the upper surface 124 of the wafer support 110). The gas distribution ports may provide process gases through one or more plenums within the showerhead 104, which may then flow into a space between the showerhead 104 and the pedestal assembly 108. Thus, a wafer 106, which may be supported on the wafer support 110 of the pedestal assembly 108, may be exposed to process gases to perform one or more processing operations.

[0066] The chamber 102 may include a plurality of lift pins 178 supported, for example, on a lift pin collar 180. In some cases, the lift pin collar 180 may be fixedly mounted relative to the chamber 102, in which case the pedestal assembly 108 may be configured to move vertically up and down relative to the chamber 102, for example, using a translation drive mechanism configured to do so. In other cases, the lift pin collar 180 may be connected to one or more vertical actuators that are used to drive the lift pins 178 vertically up and down relative to the chamber 102 (and pedestal assembly 108). In yet other embodiments, the lift pin collar 180 and the pedestal assembly 108 may both be connected to separate vertical translation systems that allow either component or assembly to move vertically independent of the other. Such a system may allow the lift pins 178 to move vertically relative to the wafer support 110, thereby lifting the wafer 106 from the wafer support 110. It will be appreciated that the showerhead 104 may similarly be configured to be vertically movable (or the pedestal assembly 108 may be understood to be movable relative to the showerhead 104) so ​​that the gap between the showerhead 104 and the pedestal assembly 108 can be widened to facilitate lifting the wafer 106 from the wafer support 110 using the lift pins 178.

[0067] 9, process gases (illustrated by gray arrows) delivered from the showerhead 104 may enter a relatively narrow space formed between the lower surface of the showerhead 104 and the upper surface 124 of the wafer support (more precisely, between the showerhead 104 and the wafer 106 supported on the wafer support 110). This narrow space, also referred to as a microvolume, reduces the amount of volume that needs to be filled with process gases to expose a wafer to the process gases, reduces the time it takes to purge such a volume, and provides a microenvironment that allows multiple wafers to be processed in a common chamber using different processes.

[0068] Concurrently with the flow of the process gas, a purge gas (shown by the white arrows) may be flowed through the pedestal assembly, for example via a first plenum volume, around the periphery of the wafer and near the wafer edge.

[0069] In some cases, pedestal assemblies as described herein may include a heating system embedded within the wafer support or be exposed to other heat sources, which may result in the wafer support reaching temperatures of several hundred degrees Celsius (e.g., 500°C or higher, 600°C or higher, or 700°C or higher). In such cases, one or more of the ring structure, substructure, wafer support, stem, tubular element, and various other components may be made of a material that can withstand such high temperatures as well as the chemical environment within the processing chamber. For example, the ring structure, substructure, wafer support, stem, and tubular element may each be made of a ceramic material (such as aluminum oxide (alumina), aluminum nitride, or other similar ceramic material). In some cases, such components may be made of different types of such materials; for example, the substructure may be aluminum oxide while the wafer support and / or ring structure may be made of aluminum nitride. In that case, it would be desirable to have a floating or non-fixed connection between these components, such as in the example above where the ring structure simply rests on top of the substructure, to accommodate the different amounts of thermal expansion in such components when transitioning between room temperature and such high temperatures.

[0070] Control of the pedestal assembly as described herein may be facilitated by the use of a controller included as part of the semiconductor processing tool having the pedestal assembly. The above-described systems may be integrated with electronics for controlling operations before and after processing of the semiconductor wafer or substrate. These electronics, referred to as a "controller," may control various components and subcomponents of the system. Depending on the processing requirements and / or system type, the controller may be programmed to control any of the systems disclosed herein, including the operation of various valves controlling the flow of purge gas and / or the exhaust of gases to pull a vacuum, the operation of heater elements within the pedestal assembly, the operation of various valves controlling the flow of process gases, the operation of a vertical lift mechanism to raise and lower the pedestal assembly and / or showerhead and / or lift pins, the electrostatic chuck or clamping electrodes, or various other components included in or provided in association with the pedestal assemblies described herein.

[0071] Generally, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, etc. Integrated circuits may include chips in firmware format 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 personalizations (or program files) that define operational parameters for performing specific operations using the pedestal assemblies described herein.

[0072] In some embodiments, the controller may be part of or coupled to a computer integrated with, coupled to, or otherwise networked to the system. For example, the controller may be in the “cloud” or all or part of a fab host computer system, enabling remote access to wafer processing. The computer may enable remote access to the system to monitor the progress of manufacturing operations, examine the history of past manufacturing operations, examine trends or performance benchmarks from multiple manufacturing operations, modify parameters of a current process, set processing steps following a current process, or initiate a new process. In some examples, a remote computer (e.g., a server) can 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 enables entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data specifying parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool the controller is configured to connect to or control. Thus, as described above, the controller may be distributed, for example, by including one or more separate controllers networked together and cooperating toward a common purpose, such as the processes and controls described herein. An example of a controller distributed for such a purpose would be one or more integrated circuits on the chamber (e.g., VTM) that are located remotely (e.g., at the platform level or as part of a remote computer) and that communicate with one or more integrated circuits that cooperate to control purge gas operation to the pedestal assembly described herein.

[0073] Without limitation, the pedestal assemblies described herein may be connected to one or more other pieces of equipment including 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 other semiconductor processing systems that may be related to or used in the fabrication and / or manufacturing of semiconductor wafers.

[0074] As noted above, depending on the process steps being performed by the tool, the controller may be in communication 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 for material transport to and from tool locations and / or load ports to transport wafer containers (e.g., FOUPs) in a semiconductor fabrication factory.

[0075] For purposes of this disclosure, the term "fluidly connected" refers to volumes, plenums, bores, etc. that are connected to each other directly or through one or more intervening components or volumes to form a fluid connection, just as the term "electrically connected" refers to components that are connected to form an electrical connection. The term "fluidly disposed" when used may be used to refer to a component, volume, plenum, or bore that is fluidly connected to at least two other components, volumes, plenums, or bores. Fluid flowing from one of those other components, volumes, plenums, and bores to another or another of those components, volumes, plenums, or bores will first flow through the "fluidly disposed" component before reaching the other or another of those components, volumes, plenums, or bores. For example, if a pump is fluidly disposed between a reservoir and an outlet, fluid flowing from the reservoir to the outlet will first flow through the pump before reaching the outlet. The term "fluidly adjacent," when used, refers to the placement of one fluid element relative to another fluid element such that there is no fluidly disposed structure between the two elements that could potentially obstruct fluid flow between the two elements. For example, in a flow path having a first valve, a second valve, and a third valve arranged in sequence, the first valve is fluidly adjacent to the second valve, the second valve is fluidly adjacent to both the first and third valves, and the third valve is fluidly adjacent to the second valve.

[0076] It is to be understood that the use of ordinal indicators (e.g., (a), (b), (c), or (1), (2), (3), etc.) in this disclosure and claims does not convey a particular order or sequence unless such order or sequence is expressly stated. For example, where there are three steps labeled (i), (ii), and (iii), it is to be understood that these steps may be performed in any order (or simultaneously, unless prohibited) unless otherwise specified. For example, if step (ii) involves manipulation of an element formed in step (i), step (ii) may be considered to have occurred some time after step (i). Similarly, it is to be understood that if step (i) involves manipulation of an element formed in step (ii), then vice versa. It is also to be understood that the use of the ordinal indicator "first" (e.g., "first item") herein should not be read as implicitly or inherently suggesting that there is necessarily a "second" instance (e.g., "second item").

[0077] As used herein, when the phrase "for each <item> of one or more <items>," "for each <item> of one or more <items>," etc. is used, it should be understood that both single items and multiple items are included, i.e., the phrase "for each..." is used in the sense that it is used in programming languages ​​to mean each and every item of all referenced items. For example, if all referenced items are single items, "each" means that single item and does not imply that there must be at least two of those items (even though dictionary definitions of "each" often define the term to mean "each of two or more things"). Similarly, it will be understood that the terms "set" or "subset" should not inherently be considered to necessarily include more than one item, and that a set or subset can include only one member or multiple members (unless the context indicates otherwise).

[0078] The term "between," as used herein in conjunction with a range of values, should be understood to include the beginning and ending values ​​of the range, unless otherwise specified. 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.

[0079] The term "operably connected" should be understood to mean a direct or indirect connection between two components and / or systems, e.g., 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 device, including a controller connected to a sub-controller of the resistive heating device that is electrically connected to a relay configured to controllably connect or disconnect the resistive heating device from a power source. The power source can provide an amount of electrical power that can be supplied to the resistive heating device to generate a desired degree of heating. It will be understood that the controller itself may not be able to directly supply such power to the resistive heating device due to the currents involved, yet still be operably connected to the resistive heating device.

[0080] It is understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes thereto will be suggested to those skilled in the art. Various details have been omitted for clarity, and various alternative designs may be implemented. As such, the examples should be considered illustrative rather than restrictive, and the disclosure should not be limited to the details described herein, but may be modified within the scope of the disclosure.

[0081] It should be understood that while the above disclosure focuses on particular exemplary embodiments, it is not limited to only the described examples but may also apply to similar modifications and arrangements, and such similar modifications and arrangements are considered to be within the scope of the present disclosure.

Claims

1. 1. An apparatus comprising: a pedestal assembly comprising a wafer support having a bottom surface and an inverted top surface, the pedestal assembly being configured to support a wafer of diameter D such that the wafer is centered on a central axis of the pedestal assembly during semiconductor processing operations; the base assembly having a first plenum volume substantially axially symmetric about the central axis of the base assembly; the first plenum volume includes a first axial sub-volume, a first radial sub-volume, and a second radial sub-volume; the first axial sub-volume fluidly connects the first radial sub-volume and the second radial sub-volume and is disposed between the first radial sub-volume and the second radial sub-volume so as to be fluidly connected therebetween; the first radial sub-volume and the second radial sub-volume both extend radially inward from the first axial sub-volume toward the central axis, the first radial sub-volume extends radially inward to a location outside a cylindrical section of diameter D centered about the central axis; the second radial sub-volume extends radially inward to a location within the cylindrical section of diameter D about the central axis; The apparatus, wherein the second radial sub-volume is farther from the top surface of the wafer support than the first radial sub-volume.

2. 10. The apparatus of claim 1, a purge inlet fluidly connected to a first plenum volume within the base assembly; the first plenum volume is configured such that when gas is flowed into the base assembly through the purge inlet, the gas flows radially outward relative to the central axis from the second radial sub-volume to the first axial sub-volume, and then from the first axial sub-volume to the first radial sub-volume before exiting the base assembly via the first radial sub-volume.

3. 3. The device according to claim 1 or 2, The apparatus, wherein the second radial sub-volume is free from obstructions for a total arc of at least 320° about the central axis.

4. 3. The device according to claim 1 or 2, The base assembly includes: a ring structure having a peripheral wall portion and a flange portion, the flange portion extending radially inward from the peripheral wall portion to a nominally circular opening having a diameter greater than D; a lower structure having an annular portion, the lower structure having a top surface facing away from the bottom surface of the wafer support; the first axial sub-volume is radially disposed between the peripheral wall portion and an outermost surface of the wafer support; the first radial sub-volume is disposed between the flange portion and the wafer support; The apparatus, wherein the second radial sub-volume is disposed between the base structure and the wafer support.

5. 5. The apparatus of claim 4, The base includes a plurality of bosses extending from the top surface of the base and contacting the bottom surface of the wafer support.

6. 6. The apparatus of claim 5, the plurality of bosses occupy a total arc of less than 40° about the central axis.

7. 6. The apparatus of claim 5, Each boss has a corresponding lift pin hole therethrough; each boss having a contact surface that contacts the wafer support; The contact surface of each boss and the portion of the wafer support that contacts that boss at the contact surface are both flat.

8. 5. The apparatus of claim 4, the first plenum volume further includes a second axial sub-volume; the second radial sub-volume is disposed in fluid communication between the first axial sub-volume and the second axial sub-volume; the substructure further comprises a tubular portion having an upper end adjacent the annular portion; the tubular portion supports the annular portion; The second axial sub-volume is at least partially surrounded by an inner surface of the tubular portion.

9. 9. The apparatus of claim 8, further comprising a first compliant seal element and a support collar; the first compliant seal element is in a load path that includes the tubular portion and spans between the support collar and the annular portion of the substructure; The apparatus wherein the first compliant seal element applies a compressive load to the annular portion of the base structure, thereby pressing the base structure against the wafer support.

10. 10. The apparatus of claim 9, the first plenum volume further includes a second axial sub-volume; the second radial sub-volume is fluidly disposed between the first axial sub-volume and the second axial sub-volume.

11. 9. The apparatus of claim 8, the pedestal assembly further comprising a second plenum volume, one or more vacuum outlets, and one or more vacuum ports; the second plenum volume is fluidly isolated from the first plenum volume within the base assembly; the one or more vacuum ports leading from the bottom surface of the wafer support to the top surface of the wafer support; the second plenum volume fluidly connects the one or more vacuum ports and the one or more vacuum outlets and is fluidly disposed between the one or more vacuum ports and the one or more vacuum outlets.

12. 12. The apparatus of claim 11, Further comprising a tubular element; The apparatus, wherein the second plenum volume is partially enclosed by the tubular element.

13. 13. The apparatus of claim 12, Further equipped with a stem, the stem supports the wafer support; the tubular element surrounds the stem; The second plenum volume is further at least partially enclosed by the stem.

14. 13. The apparatus of claim 12, further comprising a first compliant seal element, a second compliant seal element, and a support collar; the first compliant seal element is in a first load path that includes the tubular portion and extends between the support collar and the annular portion of the substructure; the second compliant seal element is in a second load path that includes the tubular portion and also extends between the support collar and the annular portion of the substructure; the first compliant seal element applies a compressive load to the annular portion of the base structure, thereby pressing the base structure against the wafer support; the second compliant seal element is positioned to apply a compressive load to the annular portion of the base, thereby similarly pressing the base against the wafer support.

15. 5. The device according to claim 4, The apparatus, wherein the ring structure, the substructure, and the wafer support are all made of a ceramic material.

16. 16. The apparatus of claim 15, The apparatus, wherein the ring structure is made of aluminum nitride and the substructure is made of aluminum oxide.

17. 10. The apparatus of claim 1, the wafer support further includes a plurality of low contact area (LCA) features distributed across a portion of the top surface of the wafer support; Each LCA feature is a protrusion from a recessed portion of the top surface of the wafer support.

18. 10. The apparatus of claim 1, 10. The apparatus, further comprising: a showerhead configured to direct one or more process gases toward the top surface of the wafer support when the one or more process gases are flowed through the showerhead.

19. 19. The apparatus of claim 18, further comprising a semiconductor processing chamber; The wafer support is located within the semiconductor processing chamber.

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