Dual Plenum Fractal Shower Head

Abstract

A dual plenum fractal (DPF) showerhead is provided for distributing different semiconductor process gases across a semiconductor wafer during processing. The DPF showerhead may have multiple layers, each layer having a pattern of gas distribution structures that are generally similar in shape to, but smaller in size than, the gas distribution structures in the layer immediately upstream. This "fractal" structure of gas flow passages allows for highly uniform distribution of process gases across the surface of a semiconductor wafer during processing, thereby improving wafer uniformity.

Description

[Background technology]

[0001] [Incorporated by reference] A PCT application form is being filed concurrently herewith as part of this application. Each application to which this application claims benefit or priority, identified in the concurrently filed PCT application form, is hereby incorporated by reference in its entirety for all purposes.

[0002] Semiconductor manufacturing tools often include a "showerhead" for distributing and delivering semiconductor process gases over semiconductor wafers being processed. Such showerheads typically include an open plenum space within the showerhead, e.g., a cylindrical volume having a diameter at least equal to the diameter of the wafer being processed, which is fluidly connected to a number of gas distribution ports located on the underside of the showerhead. In some such tools, the showerhead may be configured to distribute two different process gases over the wafer being processed.

[0003] This specification discloses a new dual gas showerhead design for use in semiconductor processing tools. Summary of the Invention

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

[0005] In some implementations, a semiconductor processing apparatus is provided that includes a showerhead. The showerhead may include a body, a first plenum inlet, a second plenum inlet, a plurality of first gas distribution holes, and a plurality of second gas distribution holes. The body may include a plurality of layers, the plurality of layers including a suitable subset of two or more fractal layers, each of the fractal layers including a set of first radially symmetric gas distribution structures and a set of second radially symmetric gas distribution structures. Each of the first radially symmetric gas distribution structures may include a first hub plenum, a plurality of first spoke passages fluidly connected to and extending radially outward from the first hub plenum, and a plurality of first riser ports, each of the first riser ports being located at a distal end of one of the first spoke passages. Each of the second radially symmetric gas distribution structures may include a second hub plenum, a plurality of second spoke passages fluidly connected to and extending radially outward from the second hub plenum, and a plurality of second riser ports, each of the second riser ports being located at a distal end of one of the second spoke passages. For each fractal layer of the fractal layers, each of the first radially symmetric gas distribution structures in that fractal layer may be positioned such that the corresponding first hub plenum is located below a first riser port in an immediately upstream layer, and each of the second radially symmetric gas distribution structures in that fractal layer may be positioned such that the corresponding second hub plenum is located below a second riser port in an immediately upstream layer.

[0006] In some implementations, one of the fractal layers may further include a set of first partially radially symmetric gas distribution structures, each of the first partially radially symmetric gas distribution structures including a first hub plenum to which a fewer number of first spoke passages are fluidly connected than any of the first radially symmetric gas distribution structures in that fractal layer.

[0007] In some further such implementations, the body may further include a feed layer immediately upstream of the fractal layer having the first set of partially radially symmetric gas distribution structures. In such implementations, the feed layer may include a plurality of first feed plenums, each including one or more first feed spoke passages fluidly connected thereto, each first feed spoke passage including a first feed riser port at a distal end thereof, each first feed riser port positioned above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer immediately downstream of the feed layer. In such an implementation, the first supply spoke passages having first supply riser ports fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer located immediately downstream of the supply layer may each have a first length, and the first supply spoke passages having first supply riser ports fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer located immediately downstream of the supply layer may each have a length longer than the first length.

[0008] In some further such implementations or some other such implementations, the fractal layer having the first set of partial radially symmetric gas distribution structures may further include a set of second partial radially symmetric gas distribution structures, each of the second partial radially symmetric gas distribution structures including a second hub plenum having a fewer number of second spoke passages than any of the second radially symmetric gas distribution structures in that fractal layer.

[0009] In some such implementations, the body may further include a feed layer immediately upstream of the fractal layer having the first set of partially radially symmetric gas distribution structures and the second set of partially radially symmetric gas distribution structures. In such an implementation, the supply layer may include a plurality of first supply plenums and a plurality of second supply plenums, each of the first supply plenums including one or more first supply spoke passages fluidly connected to the respective first supply plenum, each of the second supply plenums including one or more second supply spoke passages fluidly connected to the respective second supply plenum, each of the first supply spoke passages including a first supply riser port at a distal end, each of the second supply spoke passages including a second supply riser port at a distal end, each of the first supply riser ports located above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer located immediately downstream of the supply layer, and each of the second supply riser ports located above and fluidly connected to a corresponding one of the second hub plenums in the fractal layer located immediately downstream of the supply layer.In such implementations, the first supply spoke passages having first supply riser ports fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer may each have a first length; the first supply spoke passages having first supply riser ports fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer may each have a length longer than the first length; the second supply spoke passages having second supply riser ports fluidly connected to a second hub plenum of the second radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer may each have a second length; and the second supply spoke passages having second supply riser ports fluidly connected to a second hub plenum of the second partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer may each have a length longer than the second length.

[0010] In some implementations, the first radially symmetric gas distribution structures in the fractal layer may each include four first spoke passages, and the second radially symmetric gas distribution structures in the fractal layer each include four second spoke passages.

[0011] In some further such implementations, the first spoke passages and the second spoke passages of the first radially symmetric gas distribution structure and the second radially symmetric gas distribution structure, respectively, in at least one of the fractal layers may be at the same height.

[0012] In some further or other such implementations, each of the first spoke passages may be aligned with one of two orthogonal first passage axes, and each of the second spoke passages may be aligned with one of two orthogonal second passage axes, and the first passage axes may be 45° out of phase with the two passage axes (or at a 45° angle with respect to the second passage axis).

[0013] In some further or other such implementations, for each fractal layer among the fractal layers where there is an immediately upstream fractal layer, the first radially symmetric gas distribution structures of that fractal layer may each have a center-to-center spacing between corresponding first riser ports that is approximately 50% of the corresponding center-to-center spacing between first riser ports in the first radially symmetric gas distribution structures of the immediately upstream fractal layer.

[0014] In some further or other such implementations, for each fractal layer among the fractal layers where there is an immediately upstream fractal layer, the second radially symmetric gas distribution structures of that fractal layer may each have a center-to-center spacing between corresponding second riser ports that is approximately 50% of the corresponding center-to-center spacing between second riser ports in the second radially symmetric gas distribution structure of the immediately upstream fractal layer.

[0015] In some implementations, at least three fractal layers may be provided.

[0016] In some implementations, the body may be formed from a ceramic material.

[0017] In some further such implementations, the body may be formed from multiple individual layers of ceramic material that are fused together.

[0018] In some further or other such implementations, the body may be a 3D printed structure.

[0019] In some implementations, the apparatus may further include a processing chamber and a pedestal, wherein the pedestal is located within the processing chamber and the showerhead is located within the processing chamber above the pedestal. [Brief explanation of the drawings]

[0020] Various implementations disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals indicate like elements.

[0021] [Figure 1] FIG. 1 is an isometric view of an exemplary dual plenum fractal showerhead.

[0022] [Figure 2] FIG. 2 is an isometric view of the exemplary dual plenum fractal showerhead of FIG. 1 from the opposite side.

[0023] [Figure 3] FIG. 3 is a top view of the exemplary dual plenum fractal showerhead of FIG. [Figure 4] FIG. 4 is a bottom view of the exemplary dual plenum fractal showerhead of FIG.

[0024] [Figure 5] FIG. 5 is an exploded isometric view of the exemplary dual plenum fractal showerhead of FIG.

[0025] [Figure 6] FIG. 6 is a detailed view of an exemplary first radially symmetric gas distribution structure.

[0026] [Figure 7]FIG. 7 is a detailed view of an exemplary first radially symmetric gas distribution structure.

[0027] [Figure 8] FIG. 8 shows a size comparison of a set of radially symmetric gas distribution structures in each of the three different fractal layers.

[0028] [Figure 9] FIG. 9 is a diagram for understanding the relative proportions of the gas distribution structures of different fractal layers.

[0029] [Figure 10] FIG. 10 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG. [Figure 11] FIG. 11 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG. [Figure 12] FIG. 12 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG. [Figure 13] FIG. 13 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG. [Figure 14] FIG. 14 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG. [Figure 15] FIG. 15 is a plan view of the various layers of the exemplary dual plenum fractal showerhead of FIG.

[0030] [Figure 16] FIG. 16 is an isometric view of one of the plenum volumes in the exemplary dual plenum fractal showerhead of FIG.

[0031] [Figure 17] FIG. 17 is an isometric view of the other of the plenum volumes in the exemplary dual plenum fractal showerhead of FIG.

[0032] [Figure 18]FIG. 18 is an isometric view of both plenum volumes in the exemplary dual plenum fractal showerhead of FIG.

[0033] [Figure 19] FIG. 19 is a schematic diagram of a semiconductor processing chamber equipped with a showerhead as described herein.

[0034] 1-18 are drawn to scale within each figure, but the scale may vary from figure to figure. These figures merely illustrate one example of the concepts described herein. As will be readily appreciated, the concepts described herein may be embodied in many alternative implementations, all of which are considered within the scope of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0035] Importantly, the concepts described herein are not limited to any one aspect or implementation described herein, nor are they limited to any combinations and / or permutations of such aspects and / or implementations. Moreover, each of the aspects and / or implementations of the present invention may be used alone or in combination with one or more of the other aspects and / or implementations of the present invention. For the sake of brevity, many of these permutations and combinations are not individually described and / or illustrated herein.

[0036] The dual-plenum fractal showerheads described herein may be configured to uniformly distribute process gases to a processing volume located above a semiconductor wafer in a semiconductor processing chamber. Such dual-plenum fractal (DPF) showerheads may achieve various advantages over conventional dual-plenum showerheads. For example, because the DPF showerhead designs described herein do not have a large plenum, e.g., a generally circular plenum spanning the entire area where the showerhead's gas distribution holes are located, the amount of process gas that needs to be introduced into the showerhead for delivery through the showerhead's gas distribution ports may be significantly reduced compared to conventional open-plenum volume showerheads. Another advantage is that the fractal nature of the various flow paths in the DPF showerhead allows the flow paths to each gas distribution port in a given plenum of the DPF showerhead to have equal, or at least very similar, flow resistances, thereby reducing or eliminating variations in the time it takes for gas introduced into that plenum via a gas inlet to reach any given gas distribution port in that plenum. For example, gases flowing through the plenum of a fractal showerhead generally experience essentially the same fluid flow path characteristics, regardless of which gas distribution port they ultimately flow to. For example, after reaching the fractal layer (described in more detail below) of such a showerhead, gases may flow through a continuous gas flow path with flow path segments having similar lengths, cross-sectional shapes, and areas progressing in the same manner. This may promote more uniform wafer processing because the entire surface of the wafer is exposed to the process gases at approximately the same time, as opposed to showerheads in which, for example, process gases exit the center of the showerhead and then exit the periphery a short time later. Another advantage of the DPF showerheads described herein is that they may be fabricated from a variety of materials, including metals (e.g., stainless steel, aluminum) and ceramics (e.g., alumina, silicon oxide).

[0037] In general, a DPF showerhead as described herein may have two patterns of gas distribution holes on the underside of the showerhead, one for each plenum. In the example DPF described below, the two patterns are generally square patterns that are 45° out of phase with each other (and some instances of gas distribution holes are omitted at the corners of each square pattern, e.g., a 4×4 subpattern of gas distribution holes is omitted at each corner of each pattern). This 45° out-of-phase arrangement may be carried over to the internal layout of the various flow channels that partially define the two gas distribution plenums in the example DPF showerhead. This allows for very dense packing of gas channels within the DPF showerhead and a reduced pitch of gas distribution holes, thereby providing finer distribution of process gases across the semiconductor wafer.

[0038] DPF showerheads can be used in both asynchronous and synchronous modes. Asynchronous mode refers to alternately flowing process gas into each plenum at different times, while synchronous mode refers to simultaneously flowing process gas into both plenums. In yet another example, DPF showerheads can be used in a hybrid mode, where one plenum is continuously flowing process gas and the other plenum is alternately or cyclically flowing two or more different gases. The former is applicable, for example, to atomic layer deposition and other processes that alternate process gas application, where the smaller volume of the DPF showerhead compared to a conventional showerhead can reduce the delay time until the desired amount of process gas is delivered to the wafer, potentially reducing the overall time for each gas dosage cycle (thus reducing processing time / increasing throughput). The latter may be applicable, for example, to a process in which two process gases are simultaneously flowed into a processing space above a semiconductor wafer to react with each other to achieve a desired processing effect on the wafer. In this case, the high simultaneous supply capacity of the DPF showerhead may reduce the occurrence of a situation in which one reactant is present in the wafer processing space without the other reactant being present. In particular, the DPF showerhead described herein may be useful for processes such as those described in U.S. Patent Application No. 62 / 767,198 (entitled "METHODS FOR MAKING HARD MASKS USEFUL IN NEXT-GENERATION LITHOGRAPHY," filed November 14, 2018) and U.S. Patent Application No. 62 / 868,710 (entitled "EUV PHOTORESIST WITH MULTIPLE EUV-ABSORBING ELEMENTS AND VERTICAL COMPOSITION GRADIENT," filed June 28, 2019). The entire contents of both applications are incorporated herein by reference.

[0039] Figure 1 is an isometric view of an exemplary dual plenum fractal (DPF) showerhead. Figure 2 is an isometric view of the exemplary DPF showerhead of Figure 1 from the opposite side. Figures 3 and 4 are top and bottom plan views of the same exemplary DPF showerhead of Figure 1.

[0040] Externally, the DPF showerhead 100 of FIG. 1 is similar to many other dual-plenum showerheads. That is, it has a generally circular shape, a plurality of gas inlets (e.g., first plenum inlet 102 and a plurality (four) second plenum inlets 104) on its top surface, and two hole patterns (e.g., first hole pattern 112 and second hole pattern 114 of gas distribution holes, each including first gas distribution holes 106 and second gas distribution holes 108) on its bottom surface. Note that both first hole pattern 112 and second hole pattern 114 are in the form of generally rectangular (or, more precisely, square) arrays, but the two rectangular arrays are oriented 45° out of phase with each other. Also, there is one additional first gas distribution hole 106 that is not part of the rectangular first hole pattern 112, but this additional first gas distribution hole 106 is located in the center of the DPF showerhead 100. In most conventional showerheads, the hole pattern of gas distribution holes is typically constrained to have a generally circular outer shape. That is, the hole pattern extends outward to a circular boundary, and all of the gas distribution holes for a given plenum are located within that circular boundary and are generally evenly distributed within that boundary. However, the exemplary DPF showerhead is not configured in this manner (although, as described in more detail below, such a configuration is possible). As can be seen, the first gas distribution holes 106 and the second gas distribution holes 108 are generally evenly distributed within a circular wafer overlap region 110 (in this case, the wafer overlap region 110 has the same size as a semiconductor processing wafer typically placed beneath the DPF showerhead during processing, e.g., a 300 mm diameter (although in some implementations such an even hole distribution may be maintained over a circular region of, e.g., a larger diameter, to achieve uniform gas distribution to and beyond the periphery of the wafer during processing)). However, there are portions of both the first hole pattern 112 and the second hole pattern 114 that extend beyond the wafer overlap region 110. The first gas distribution holes 106 and the second gas distribution holes 108 located outside the wafer overlap region 110 are no longer evenly distributed relative to each other.As will become apparent from the description below, in the exemplary DPF showerhead, gas distribution ports located outside the wafer overlap region 110 are included to allow the various gas distribution structures of each plenum in various layers within the DPF showerhead to be the same design for each layer. It should be understood that, with appropriate modifications, a DPF showerhead may be provided with reduced or eliminated gas distribution ports located outside the wafer overlap region 110, for example, by using variably designed gas distribution structures near the periphery of the DPF showerhead 100 in these layers. Such alternative implementations are also considered within the scope of the present disclosure.

[0041] In an exemplary implementation, the array spacings d1 and d2 of the first hole pattern 112 and the second hole pattern 114, respectively, are:

number

[0042] FIG. 5 is an exploded isometric view of the example DPF showerhead of FIG. 1. As can be seen from this exploded view, the DPF showerhead 100 may be divided into several different layers 116, each having a different gas distribution structure. It will be appreciated that such a DPF showerhead 100 may be created, for example, by machining or otherwise forming each layer as a separate component and then bonding or fusing the various layers into a laminate stack to form the DPF showerhead. However, in other implementations, other techniques may be used to produce equivalent structures, such as "3D printing" a DPF showerhead structure from metal, ceramic, or other materials using additive manufacturing.

[0043] In this description, references to layers “upstream” of a particular layer are understood to refer to layers closer to the “top” of the DPF showerhead 100, e.g., closer to the first plenum inlet 102 or the second plenum inlet 104. References to layers “downstream” of a particular layer are understood to refer to layers closer to the “bottom” of the DPF showerhead 100, e.g., closer to the first gas distribution holes 106 or the second gas distribution holes 108. References to layers “immediately upstream” of a particular layer refer to the layer most upstream of that particular layer, and references to layers “immediately downstream” of that particular layer similarly refer to the layer most downstream of that particular layer. Also, although a given showerhead may be arbitrarily divided into multiple layers in any manner deemed appropriate, references to “layers” herein are understood to refer to the layers as shown in FIG. 5 . For example, each layer may have vertical holes (or gas distribution holes) on one side and gas flow paths / plenums on the other side, with each riser port / gas distribution hole in a layer terminating in one of the gas flow paths (the inlet layer may be an exception to this, as it only has vertical holes therein as the first plenum inlet 102 and second plenum inlet 104).

[0044] The various layers 116 may include, for example, an inlet layer 118 (including layer 116a), a feed layer 120 (including, for example, layers 116b and 116c), and a fractal layer 122 (including, for example, layers 116d, 116e, and 116f). The inlet layer 118 may include, for example, through-holes or other structures, such as first plenum inlet 102 and second plenum inlet 104, that can introduce process gases into the plenum of the DPF showerhead 100.

[0045] The supply layer 120 may include, for example, a layer 116b that includes the first supply passage 124 and the second supply passage 126. Each of these layers may fluidly connect one of the first plenum inlet 102 or the second plenum inlet 104 with a corresponding first supply riser port 138 or second supply riser port 140, respectively, within the layer 116b. The first supply riser port 138 and the second supply riser port 140 in the layer 116b 140 may pass through the bottom of layer 116b and fluidly connect one of first supply passages 124 or second supply passages 126, respectively, with first supply plenum 130 or second supply plenum 132 in layer 116c.

[0046] One of the supply layers 120, layer 116c, may have multiple gas distribution structures. Each gas distribution structure generally takes the form of a central plenum with multiple supply spoke passages extending outward. For example, layer 116c may have multiple first supply plenums 130 (four shown, but other numbers are possible, typically equal to the number of first supply riser ports 138 in the immediately upstream layer 116). Similarly, layer 116c may have multiple second supply plenums 132 (four shown, but other numbers are possible, typically equal to the number of second supply riser ports 140 in the immediately upstream layer 116).

[0047] Each first supply plenum 130 may have a plurality of first supply spoke passages 134 extending radially outward from that first supply plenum 130. Each first supply spoke passage 134 may terminate in a corresponding first supply riser port 138 in layer 116c that leads to the immediately downstream layer 116 (e.g., layer 116d). Similarly, each second supply plenum 132 may have a plurality of second supply spoke passages 136 extending radially outward from that second supply plenum 132. Each second supply spoke passage 136 may terminate in a corresponding second supply riser port 140 in layer 116c that leads to the immediately downstream layer 116. Each first supply riser port 138 and second supply riser port 140 in layer 116c that leads to the immediately downstream layer 116. supply The riser port 140 may be positioned so as to be approximately centered over the corresponding plenum structure of the immediately downstream layer.

[0048] It should be noted that the supply spoke passages radiating from each supply plenum do not necessarily have the same flow resistance due to differences in the supply spoke passage geometry, as will be explained in more detail below.

[0049] Also note that the supply passages and supply spoke passages shown in FIG. 5 each include two internal support walls 128. The internal support walls 128 generally extend along the length of the passages, from one end to the other. Such support walls 128 (or other structures) may be included optionally in some implementations, for example. For example, if the DPF showerhead 100 is made of green-machined ceramic layers that are stacked and then fired in a kiln to form a single, fused and hardened ceramic part, it may be desirable for wider passages to include one or more internal support walls 128 (or other support structures) to mechanically support the layers that form the “top” of such passages. With other shapes and / or other manufacturing techniques, such support walls 128 may not be necessary.

[0050] The process gas flowing through the distribution layer 120 is then directed to the fractal layers 122. Each fractal layer 122 generally comprises identical, repeating radially symmetric gas distribution structures (or portions thereof) for each plenum, with the radially symmetric gas distribution structures in each layer immediately downstream of a layer being scaled down from the corresponding radially symmetric gas distribution structure in that layer. In this example, each radially symmetric gas distribution structure in a layer is scaled down by approximately 50% from the corresponding radially symmetric gas distribution structure in the immediately upstream layer. However, other implementations may use different scaling factors. Figure 8 provides a size comparison of the sets of radially symmetric gas distribution structures in each of the three fractal layers 122 shown in Figure 5. Each set of radially symmetric gas distribution structures is shown to scale with respect to the other sets of radially symmetric gas distribution structures shown. As can be seen from the dashed dotted lines passing through the centers of selected riser ports in each set of radially symmetric gas distribution structures, the center-to-center spacing of the vertical holes in each set of radially symmetric gas distribution structures is reduced by 50% in each fractal layer 122 compared to the set of radially symmetric gas distribution structures immediately upstream.

[0051] This characteristic gives the gas distribution passages of each plenum in the DPF showerhead a "fractal" appearance, hence the name "dual plenum fractal showerhead." Note that in some implementations, particular substructures in each radially symmetric gas distribution structure may be scaled up or down from corresponding structures in the radially symmetric gas distribution structure of the immediately upstream layer. For example, in the exemplary DPF showerhead 100, the center-to-center distance between the riser ports of a given radially symmetric gas distribution structure is 1 / 2 the center-to-center distance between the riser ports of the immediately upstream layer. Upstream 50% of the corresponding center-to-center distance between riser ports of the radially symmetric gas distribution structure, provided that the cross-sectional width of each spoke passage is UpstreamThe center-to-center spacing of the radially symmetric gas distribution structures 146 and 148 may actually increase. Figure 9 provides additional insight into this characteristic. In Figure 9, three sets of one first radially symmetric gas distribution structure 146 and four adjacent second radially symmetric gas distribution structures 148 (a set from each of the three fractal layers 122) are scaled so that the center-to-center spacing between their respective vertical holes is the same and they are centered relative to one another. As can be seen, the first and second radially symmetric gas distribution structures 146' and 148' (shown in dotted outline) of layer 116e have slightly wider spoke passages (relative to the center-to-center spacing between the vertical holes) than the corresponding first and second radially symmetric gas distribution structures 146 and 148. Similarly, the first and second radially symmetric gas distribution structures 146" and 148" (shown in dashed outline) of layer 116f have spoke passages that are slightly wider (relative to the center-to-center distance between vertical holes) than the corresponding first and second radially symmetric gas distribution structures 146' and 148'.

[0052] It is further understood that the size of the diameters of the first and second vertical holes of each radially symmetric gas distribution structure relative to the center-to-center spacing may differ between radially symmetric gas distribution structures in fractal layers immediately upstream / downstream of each other.

[0053] In some implementations, a portion of the radially symmetric gas distribution structure of one or more fractal layers 122 may be provided in a "partial configuration," i.e., with only a portion of the radially symmetric gas distribution structure present. For example, the radially symmetric gas distribution structures in the exemplary DPF showerhead are +-shaped or X-shaped, each with four spoke passages extending radially outward from a hub plenum. In this case, the partial radially symmetric gas distribution structure may have a similar configuration but may lack one or two of the spoke passages.

[0054] For example, in layer 116d, a plurality of first radially symmetric gas distribution structures 146 and a plurality of second radially symmetric gas distribution structures 148 are provided, each of which is either +-shaped or X-shaped (note, however, that the first radially symmetric gas distribution structures 146 are larger than the second radially symmetric gas distribution structures 148; see the above discussion regarding array spacing). Each of the first radially symmetric gas distribution structures 146 and the second radially symmetric gas distribution structures 148 has a corresponding hub plenum and a plurality of spoke passages extending radially outward therefrom.

[0055] FIG. 6 illustrates an exemplary first radially symmetric gas distribution structure 146, and FIG. 7 illustrates an exemplary second radially symmetric gas distribution structure 148. FIGS. 6 and 7 are drawn to the same scale. As can be seen, the first radially symmetric gas distribution structure 146 includes a first hub plenum 158. The first hub plenum 158 may be positioned directly below and fluidly connected to a corresponding first riser port 162′ (or, in some examples, the first supply riser port 138) in the immediately upstream layer 116. The first hub plenum 158 may include a plurality (four in this example) of first spoke passages 154 extending radially outward from the first hub plenum 158 in a radially symmetric manner. Each first spoke passage 154 may terminate in a corresponding first riser port 162 (or, in the case of the downstream-most layer 116, a corresponding first gas distribution hole 106).

[0056] Similarly, the second radially symmetric gas distribution structure 148 shown in FIG. 7 includes a second hub plenum 160. The second hub plenum 160 may be positioned directly below and fluidly connected to a corresponding second riser port 164′ (or, in some examples, the second supply riser port 140) in the immediately upstream layer 116. The second hub plenum 160 may have a plurality (four in this example) of second spoke passages 156 extending radially symmetrically radially outward from the second hub plenum 160. Each second spoke passage 156 may terminate in a corresponding second riser port 164 (or, in the case of the downstream-most layer 116, a corresponding second gas distribution hole 108).

[0057] 5, note that the first radially symmetric gas distribution structure 146 and the second radially symmetric gas distribution structure 148 generally occupy the central region of layer 116d, while the first partial radially symmetric gas distribution structure 142 and the second partial radially symmetric gas distribution structure 144 are employed near the periphery of layer 116d. Each of the first partial radially symmetric gas distribution structures 142 has only two first spoke passages 154, and each of the second partial radially symmetric gas distribution structures 144 has only three second spoke passages 156. The remaining fractal layers 122 in this example include only radially symmetric gas distribution structures and do not include partial radially symmetric gas distribution structures. However, in other implementations, other fractal layers 122 may include partial radially symmetric gas distribution structures as well.

[0058] While the structure of the exemplary DPF showerhead 100 is clearly shown in the figures above, Figures 10-15 are now used to illustrate plan views of layers 116a-f of the exemplary dual plenum fractal showerhead of Figure 1. These figures overlap somewhat with the figures above, but further illustrate the structure and may be referenced, inter alia, in the following description.

[0059] When a partial radially symmetric gas distribution structure is used, flow imbalances may occur in the illustrated DPF showerhead unless certain mitigation measures are taken. For example, if the same amount of process gas is supplied to each hub plenum of a radially symmetric gas distribution structure at the same gas flow rate as for the corresponding partial radially symmetric gas distribution structure, each riser port of the partial radially symmetric gas distribution structure will have an increased gas flow rate compared to the riser ports of the radially symmetric gas distribution structure. This is because the partial radially symmetric gas distribution structure has fewer spoke passages and corresponding riser ports compared to the radially symmetric gas distribution structure. Therefore, compared to the riser ports of the radially symmetric gas distribution structure, the total cross-sectional area of ​​the riser ports of the partial radially symmetric gas distribution structure is smaller, and as a result, a larger amount of gas will flow through each riser port of the partial radially symmetric gas distribution structure compared to the riser ports of the radially symmetric gas distribution structure. This is undesirable because downstream radially symmetric gas distribution structures in subsequent layers 116 that are fed by partial radially symmetric gas distribution structures will receive a disproportionate amount of gas compared to radially symmetric gas distribution structures in those downstream layers that are fed by radially symmetric gas distribution structures, ultimately resulting in uneven gas delivery through the gas distribution holes.

[0060] To mitigate or prevent such effects, the supply passages supplying process gas to the partial radially symmetric gas distribution structure immediately downstream from a supply riser port may be designed to be longer than the supply passages supplying process gas to the radially symmetric gas distribution structure immediately downstream from that same supply riser port. For example, in FIG. 12 , two of the three first supply spoke passages 134 radially extending from each first supply plenum 130 are seen to be approximately twice as long as the remaining first supply spoke passages 134 radially extending from each first supply plenum 130. This increased length increases the flow resistance of these first supply spoke passages 134, thereby causing the flow rate to the first supply riser ports 138 located at the ends of these first supply spoke passages 134 to be approximately half the flow rate at the first supply riser ports 138 of the remaining first supply spoke passages 134 radially extending from each first supply plenum 130. Similarly, one of the four second supply spoke passages 136 extending radially from each second supply plenum 132 has a longer length compared to the other second supply spoke passages 136 extending radially from each second supply plenum 132. This may have a similar effect, reducing the fluid flow experienced by the partial radially symmetric gas distribution structure of the immediately downstream layer, which has only three spokes, thereby more uniforming the gas flow from the DPF showerhead 100.

[0061] After the gas reaches each gas distribution structure, the gas flow may be divided approximately evenly among the various spoke passages in that distribution structure before moving on to the next set of gas distribution structures in the immediately downstream layer (or out the gas distribution ports). This repeated dividing property serves to distribute the process gas evenly over a large area of ​​the showerhead. In this example, three fractal layers 122 are provided, although more or fewer such layers may be used depending on how finely or coarsely the gas is desired to be distributed.

[0062] In the exemplary DPF showerhead 100, the radially symmetric gas distribution structures in a given fractal layer 122 of each plenum can be seen to have spoke passages aligned with passage axes that are 45° out of phase with each other. For example, in fractal layer 116d of FIG. 5, first radially symmetric gas distribution structure 146 has first spoke passages 154 aligned with first passage axis 150, and second radially symmetric gas distribution structure 148 has second spoke passages 156 aligned with second passage axis 152. And, as can be seen, first passage axis 150 and second passage axis 152 are 45° out of phase with each other.

[0063] Figure 16 is an abstract isometric view of one of the plenum volumes in the example dual plenum fractal showerhead of Figure 1. Figure 17 is an abstract isometric view of the other of the plenum volumes in the example dual plenum fractal showerhead of Figure 1. Figure 18 is an abstract isometric view of both plenum volumes in the example dual plenum fractal showerhead of Figure 1.

[0064] 16-18, it can be readily seen that the hub plenum of each radially symmetric or partially radially symmetric gas distribution structure in each fractal layer is fluidly connected to a riser port at the distal end of one of the spoke passages (or a feed riser port in one of the feed layers 120) that radiate from the hub plenum of the radially symmetric gas distribution structure in the immediately upstream fractal layer. The 45° phase shift of the radial spoke passages of each plenum in each layer also allows for a very high density of gas distribution holes in the bottom surface of the DPF showerhead while maintaining approximately equal flow resistance from the inlet of any plenum to any gas distribution port. For example, such a configuration allows each of the various second spoke passages 156 to extend partially into the space between two adjacent first spoke passages 154, thereby allowing each corresponding second riser port 164 (or second gas distribution hole 108 of layer 116f) to be located midway along a line between the two first riser ports 162 (or first gas distribution holes 106) closest to that second riser port.

[0065] Also, in the exemplary DPF showerhead, multiple gas distribution holes and / or radially symmetric gas distribution structures are present outside the wafer overlap region 110. Therefore, it should be noted that process gas supplied from these likely will not actually reach the wafer, since it will generally tend to be pushed outward, away from the wafer, by process gas supplied from the radially symmetric gas distribution structure and / or gas distribution holes in the wafer overlap region 110. Therefore, process gas supplied from gas distribution holes outside the wafer overlap region 110 can be considered, in effect, excess or wasted process gas. As noted above, in some implementations, the number of gas distribution holes located outside the wafer overlap region may be reduced or eliminated to reduce or eliminate the amount of excess or wasted gas generated by the DPF showerhead. However, doing so may require extensive customization of the various radially symmetric gas distribution structures used to ensure uniformity of gas flow through the gas distribution holes (indeed, they may no longer reasonably be considered “radially symmetric gas distribution structures”). By including radially symmetric gas distribution structures and / or gas distribution holes located outside the wafer overlap region 110, the flow split occurring at each radially symmetric gas distribution structure is the same for all radially symmetric gas distribution structures within the fractal layer, thereby achieving uniform flow through the gas distribution holes of each plenum without complex modifications to the radially symmetric gas distribution structures within the fractal layer 122. It should also be noted that as the overall size of the radially symmetric gas distribution structures decreases, they become increasingly susceptible to small dimensional variations, making it potentially more difficult to individually fine-tune the gas flow characteristics of each radially symmetric gas distribution structure through customization. Thus, the approach illustrated with respect to the exemplary DPF showerhead 100 results in a substantially uniform distribution of process gas across the wafer, although it may generate some excess or wasted gas.

[0066] As previously mentioned, the underside of the DPF showerhead 100 includes a single gas distribution hole, the central hole, that is not part of any hole pattern. Such a central hole may be optionally included to further enhance wafer processing uniformity, for example, it may be fluidly connected to the first plenum inlet. Depending on the specific process conditions required, it may be desirable to have the central hole the same size as the other gas distribution holes in the first plenum, or larger or smaller than these other gas distribution holes. In implementations using a central hole the same size as the other first gas distribution holes, the flow rate through the central hole may be varied in some such implementations by varying the flow resistance within the showerhead from the first gas inlet to the central hole. The central hole need not have the same flow resistance as the other first gas distribution holes in the first plenum.

[0067] Additionally, while this disclosure has primarily described dual-plenum fractal showerheads, it should be noted that similar principles may be implemented in a single-plenum fractal showerhead format, for example, by simply omitting one of the plenums and associated structure. Such single-plenum fractal (SPF) showerheads are also considered within the scope of this disclosure.

[0068] DPF (and SPF) showerheads according to the concepts described herein may be used in semiconductor processing steps, as described above. For example, a DPF or SPF showerhead may be used in a semiconductor processing chamber, such as the semiconductor processing chamber 170 of FIG. 19. Such a DPF or SPF showerhead 100 may be suspended within the chamber 170 via a shank 176. The shank 176 may include gas feed passages for supplying process gases to an inlet of the DPF or SPF showerhead for distribution across a wafer 174, which may be supportable within the chamber 170 by a pedestal 172.

[0069] In some implementations, a controller may be provided. Ra is The system may be part of a system. The system may include the examples described above and may further be operatively connected to receive information from and / or control various valves, mass flow controllers, pumps, etc. Such systems may include semiconductor processing equipment, including one or more processing tools, one or more chambers, one or more processing platforms, and / or specific processing components (such as a wafer pedestal and gas flow systems). These systems may be integrated with electronics for controlling the operation of the system before, during, and after processing of a semiconductor wafer or substrate. The electronics may also be referred to as a "controller" and may control various components or subparts of one or more systems. The controller may be programmed to control any of the processes disclosed herein depending on the processing requirements and / or type of system. These processes include the supply of various gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, flow settings, fluid supply settings, and position and operation settings for the DPF or SPF showerhead, etc., described herein.

[0070] Broadly, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software to receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. Integrated circuits may include chips as 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). The program instructions may be instructions communicated to the controller as various individual settings (or program files) that define operational parameters for performing a particular process on or for a semiconductor wafer or for a system. In some implementations, the operational parameters may be part of a recipe defined by a process engineer to accomplish one or more processing steps in the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0071] In some implementations, the controller may be part of or coupled to a computer, where the computer may be integrated with the system, coupled to the system, or otherwise networked with the system, or a combination thereof. For example, the controller may reside in the “cloud” or in all or part of a fab host computer system. This enables remote access to wafer processing. The computer may enable remote access to the system to monitor the progress of a manufacturing process, examine past manufacturing process history, or examine trends or performance indicators from multiple manufacturing processes, modify parameters for a current process, configure subsequent processing steps, or initiate a new process. In some examples, a process recipe may be provided to the system from a remote computer (e.g., a server) over a network, where the network may include a local network or the Internet. The remote computer may include a user interface that allows input or programming of parameters and / or settings. These parameters and / or settings are then communicated from the remote computer to the system. In some examples, the controller receives instructions as data, which specifies parameters for each processing step to be performed in one or more operations. It should be understood that these parameters may be specific to the type of process being performed and the type of tool the controller is configured to cooperate with or control. Thus, as described above, the controller may be distributed, such as by having one or more individual controllers that are networked and operate toward a common purpose, such as the process and control described herein. An example of a distributed controller for such a purpose includes one or more integrated circuits mounted in the chamber that communicate with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer).These integrated circuits work together to control the process in the chamber.

[0072] Non-limiting examples of systems 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 related to or usable in the fabrication and / or production of semiconductor wafers.

[0073] As described above, depending on one or more process steps being performed by the tool, the controller may communicate with one or more of other tool circuits or tool 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 and from tool locations and / or load ports within a semiconductor manufacturing factory.

[0074] For purposes of this disclosure, the term "fluidically connected" is used in reference to volumes, plenums, holes, etc. that are connectable to one another to form a fluid connection, similar to how the term "electrically connected" is used in reference to components that are connected to one another to form an electrical connection. The term "fluidically intervening" may refer to a component, volume, plenum, or hole that is fluidly connected to at least two other components, volumes, plenums, or holes, where fluid flowing from one of the at least two other components, volumes, plenums, or holes to the other or one of the remaining components first flows through the "fluidically intervening" component before reaching the other or one of the remaining components. For example, if a pump is fluidly intervening between a reservoir and an outlet, fluid flowing from the reservoir to the outlet will first flow through the pump before reaching the outlet.

[0075] Furthermore, it should be understood that the generic term "riser port" may be used herein to refer not only to the riser ports of each radially symmetric gas distribution structure, but also to supply riser ports and gas distribution holes. Thus, for example, a gas distribution hole may be described not only as a gas distribution hole, but also as a riser port. Similarly, a supply riser port may simply be referred to as a riser port. Generally, the riser ports at the bottom of a DPF or SPF showerhead (when the showerhead is installed in a processing chamber) may also be referred to as "gas distribution holes."

[0076] When phrases such as "for each <item> of one or more <items>," "for each <item> of one or more <items>," and the like are used herein, they should be understood to include both groups of single items and groups of multiple items. That is, the phrase "each" is used in the sense that the phrase is used in programming languages ​​to refer to each item, whatever the population of the referenced items. For example, if the population of the referenced items is a single item, then the term "each" refers only to that single item and does not imply that there must be at least two of those items (despite the fact that dictionaries often define the term "each" to mean "one of two or more").

[0077] It should also be understood that, in this disclosure, the term “layer” can refer to either a physically separable layer (e.g., a layer that is adhered, fused, or otherwise fixed in position relative to another layer in a laminate structure) or, more generally, to a region of a structure defined between two reference surfaces. Such a structure may be comprised of multiple components that are assembled or joined, or in some cases, may be a monolithic structure (e.g., a single-piece structure). For example, a cast or additively manufactured single-piece part may be considered to feature its distinct “layers” even though the part is not actually created by joining physically separate layers (although an argument can be made that most additively manufactured parts inherently have a layered structure, since they are typically printed one thin layer at a time). It should also be recognized that a “layer” of a part that is actually manufactured as a laminate (i.e., from individual layers) may not necessarily coincide with one of these individual layers. For example, a layer of a part may be defined to include only a portion of such an individual layer portion, a portion of two adjacent individual layer portions, or one or two non-adjacent individual layer portions and a portion of the individual layer portion between them. The present disclosure includes the following application examples: [Application example 1] 1. A semiconductor processing apparatus, comprising: a showerhead including a body, a first plenum inlet, a second plenum inlet, a plurality of first gas distribution holes, and a plurality of second gas distribution holes; the body includes a plurality of layers, the plurality of layers including a suitable subset of two or more fractal layers, each of the fractal layers including a first set of radially symmetric gas distribution structures and a second set of radially symmetric gas distribution structures; each said first radially symmetric gas distribution structure includes a first hub plenum, a plurality of first spoke passages fluidly connected to and extending radially outward from said first hub plenum, and a plurality of first riser ports, each said first riser port being located at a distal end of one of said first spoke passages; each said second radially symmetric gas distribution structure includes a second hub plenum, a plurality of second spoke passages fluidly connected to and extending radially outward from said second hub plenum, and a plurality of second riser ports, each said second riser port being located at a distal end of one of said second spoke passages; For each fractal layer of said fractal layers: each said first radially symmetric gas distribution structure in that fractal layer is positioned such that the corresponding said first hub plenum is positioned below a first riser port in the immediately upstream layer; each said second radially symmetric gas distribution structure in that fractal layer is positioned such that the corresponding said second hub plenum is positioned below a second riser port in the immediately upstream layer; Semiconductor processing equipment. [Application example 2] The semiconductor processing apparatus according to Application Example 1, one of the fractal layers further includes a set of first partially radially symmetric gas distribution structures, each of the first partially radially symmetric gas distribution structures including a first hub plenum fluidly connected to a fewer number of first spoke passages than any of the first radially symmetric gas distribution structures in that fractal layer; Semiconductor processing equipment. [Application example 3] The semiconductor processing apparatus according to Application Example 2, the body further includes a feed layer immediately upstream of the fractal layer having the first set of partially radially symmetric gas distribution structures; the supply layer includes a plurality of first supply plenums, each of the first supply plenums including one or more first supply spoke passages fluidly connected thereto, each of the first supply spoke passages including a first supply riser port at a distal end thereof, each of the first supply riser ports being located above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer immediately downstream of the supply layer; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a first length; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a length greater than the first length; Semiconductor processing equipment. [Application example 4] The semiconductor processing apparatus according to Application Example 2, the fractal layer having the first set of partial radially symmetric gas distribution structures further includes a set of second partial radially symmetric gas distribution structures, each second partial radially symmetric gas distribution structure including a second hub plenum having a fewer number of second spoke passages than any of the second radially symmetric gas distribution structures in that fractal layer; Semiconductor processing equipment. [Application example 5] The semiconductor processing apparatus according to Application Example 4, the body further includes a feed layer immediately upstream of the fractal layer having the first set of partial radially symmetric gas distribution structures and the second set of partial radially symmetric gas distribution structures; the supply layer includes a plurality of first supply plenums and a plurality of second supply plenums, each of the first supply plenums including one or more first supply spoke passages fluidly connected to each of the first supply plenums, each of the second supply plenums including one or more second supply spoke passages fluidly connected to each of the second supply plenums, each of the first supply spoke passages including a first supply riser port at a distal end, each of the second supply spoke passages including a second supply riser port at a distal end, each of the first supply riser ports being located above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer immediately downstream of the supply layer, and each of the second supply riser ports being located above and fluidly connected to a corresponding one of the second hub plenums in the fractal layer immediately downstream of the supply layer; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a first length; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer have a length greater than the first length; the second supply spoke passages each having a second supply riser port fluidly connected to a second hub plenum of the second radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a second length; the second supply spoke passages each having a second supply riser port fluidly connected to a second hub plenum of the second partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a length greater than the second length; Semiconductor processing equipment. [Application Example 6] The semiconductor processing apparatus according to Application Example 1, the first radially symmetric gas distribution structures in the fractal layer each include four first spoke passages, and the second radially symmetric gas distribution structures in the fractal layer each include four second spoke passages; Semiconductor processing equipment. [Application Example 7] The semiconductor processing apparatus according to Application Example 6, the first spoke passages and the second spoke passages of the first radially symmetric gas distribution structure and the second radially symmetric gas distribution structure in at least one of the fractal layers are at the same height; Semiconductor processing equipment. [Application Example 8] The semiconductor processing apparatus according to Application Example 6, For each fractal layer of said fractal layers: each of the first spoke passages is aligned with one of two orthogonal first passage axes; each of the second spoke passages is aligned with one of two orthogonal second passage axes; the first passage axis is 45° out of phase with the second passage axis; Semiconductor processing equipment. [Application Example 9] The semiconductor processing apparatus according to Application Example 6, for each of the fractal layers having an immediately upstream fractal layer, the first radially symmetric gas distribution structures of that fractal layer each have a center-to-center spacing between corresponding first riser ports that is about 50% of the center-to-center spacing between corresponding first riser ports in the first radially symmetric gas distribution structures of the immediately upstream fractal layer; Semiconductor processing equipment. [Application Example 10] The semiconductor processing apparatus according to Application Example 6, for each of the fractal layers having an immediately upstream fractal layer, the second radially symmetric gas distribution structures of that fractal layer each have a center-to-center spacing between corresponding second riser ports that is about 50% of the center-to-center spacing between corresponding second riser ports in the second radially symmetric gas distribution structures of the immediately upstream fractal layer; Semiconductor processing equipment. [Application Example 11] The semiconductor processing apparatus according to Application Example 1, At least three fractal layers are provided; Semiconductor processing equipment. [Application Example 12] The semiconductor processing apparatus according to Application Example 1, The body is formed from a ceramic material. Semiconductor processing equipment. [Application Example 13] The semiconductor processing apparatus according to Application Example 12, the body being formed from a plurality of individual layers of ceramic material fused together; Semiconductor processing equipment. [Application Example 14] The semiconductor processing apparatus according to Application Example 12, The body is a 3D printed structure. Semiconductor processing equipment. [Application Example 15] The semiconductor processing apparatus according to any one of Application Examples 1 to 14, a processing chamber; a base; and the pedestal is located within the processing chamber; the showerhead is positioned within the processing chamber above the pedestal; Semiconductor processing equipment.

Claims

1. 1. A semiconductor processing apparatus comprising: a showerhead including a body, a first plenum inlet, a second plenum inlet, a plurality of first gas distribution holes, and a plurality of second gas distribution holes; the body includes a plurality of layers, the plurality of layers including a subset of two or more fractal layers, each of the fractal layers including a first set of radially symmetric gas distribution structures and a second set of radially symmetric gas distribution structures; each said first radially symmetric gas distribution structure includes a first hub plenum, a plurality of first spoke passages fluidly connected to and extending radially outward from said first hub plenum, and a plurality of first riser ports, each said first riser port being located at a distal end of one of said first spoke passages; each said second radially symmetric gas distribution structure includes a second hub plenum, a plurality of second spoke passages fluidly connected to and extending radially outward from said second hub plenum, and a plurality of second riser ports, each said second riser port being located at a distal end of one of said second spoke passages; the first radially symmetric gas distribution structure and the second radially symmetric gas distribution structure are fluidly separated from each other within the body; For each fractal layer of said fractal layers: each said first radially symmetric gas distribution structure in that fractal layer is positioned such that a corresponding said first hub plenum is located below a first riser port in the immediately upstream layer; each said second radially symmetric gas distribution structure in that fractal layer is positioned such that a corresponding said second hub plenum is positioned below a second riser port in the immediately upstream layer; Semiconductor processing equipment.

2. 2. The semiconductor processing apparatus according to claim 1, one of the fractal layers further includes a set of first partially radially symmetric gas distribution structures, each of the first partially radially symmetric gas distribution structures including a first hub plenum having a fewer number of first spoke passages fluidly connected thereto than any of the first radially symmetric gas distribution structures in that fractal layer; Semiconductor processing equipment.

3. 3. The semiconductor processing apparatus according to claim 2, the body further comprises a feed layer immediately upstream of the fractal layer having the first set of partially radially symmetric gas distribution structures; the supply layer includes a plurality of first supply plenums, each of the first supply plenums including one or more first supply spoke passages fluidly connected thereto, each of the first supply spoke passages including a first supply riser port at a distal end, each of the first supply riser ports located above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer immediately downstream of the supply layer; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, the first supply spoke passages each having a first length; the first supply spoke passages having first supply riser ports fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer each have a length greater than the first length; Semiconductor processing equipment.

4. 3. The semiconductor processing apparatus according to claim 2, the fractal layer having the first set of partially radially symmetric gas distribution structures further includes a set of partially radially symmetric gas distribution structures, each of the partially radially symmetric gas distribution structures including a second hub plenum having a fewer number of second spoke passages than any of the partially radially symmetric gas distribution structures in that fractal layer; Semiconductor processing equipment.

5. 5. The semiconductor processing apparatus according to claim 4, the body further comprises a feed layer immediately upstream of the fractal layer having the first set of partially radially symmetric gas distribution structures and the second set of partially radially symmetric gas distribution structures; the supply layer includes a plurality of first supply plenums and a plurality of second supply plenums, each of the first supply plenums including one or more first supply spoke passages fluidly connected to each of the first supply plenums, each of the second supply plenums including one or more second supply spoke passages fluidly connected to each of the second supply plenums, each of the first supply spoke passages including a first supply riser port at a distal end, each of the second supply spoke passages including a second supply riser port at a distal end, each of the first supply riser ports being located above and fluidly connected to a corresponding one of the first hub plenums in the fractal layer immediately downstream of the supply layer, and each of the second supply riser ports being located above and fluidly connected to a corresponding one of the second hub plenums in the fractal layer immediately downstream of the supply layer; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, the first supply spoke passages each having a first length; the first supply spoke passages each having a first supply riser port fluidly connected to a first hub plenum of the first partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a length greater than the first length; the second supply spoke passages each having a second supply riser port fluidly connected to a second hub plenum of the second radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, the second supply spoke passages each having a second length; the second supply spoke passages each having a second supply riser port fluidly connected to a second hub plenum of the second partially radially symmetric gas distribution structure in the fractal layer immediately downstream of the supply layer, each having a length greater than the second length; Semiconductor processing equipment.

6. 2. The semiconductor processing apparatus according to claim 1, the first radially symmetric gas distribution structures in the fractal layer each include four first spoke passages, and the second radially symmetric gas distribution structures in the fractal layer each include four second spoke passages; Semiconductor processing equipment.

7. 7. The semiconductor processing apparatus according to claim 6, the first spoke passages and the second spoke passages of the first radially symmetric gas distribution structure and the second radially symmetric gas distribution structure in at least one of the fractal layers are at the same height. Semiconductor processing equipment.

8. 7. The semiconductor processing apparatus according to claim 6, For each fractal layer of said fractal layers: each of the first spoke passages is aligned with one of two orthogonal first passage axes; each of the second spoke passages is aligned with one of two orthogonal second passage axes; the first passage axis is out of phase with the second passage axis by 45°; Semiconductor processing equipment.

9. 7. The semiconductor processing apparatus according to claim 6, for each one of the fractal layers having an immediately upstream fractal layer, each of the first radially symmetric gas distribution structures of that fractal layer has a center-to-center spacing between corresponding first riser ports that is 50% of a corresponding center-to-center spacing between first riser ports in the first radially symmetric gas distribution structure of the immediately upstream fractal layer; Semiconductor processing equipment.

10. 7. The semiconductor processing apparatus according to claim 6, for each one of the fractal layers having an immediately upstream fractal layer, the second radially symmetric gas distribution structure of that fractal layer has a center-to-center spacing between corresponding second riser ports that is 50% of the center-to-center spacing between corresponding second riser ports in the second radially symmetric gas distribution structure of the immediately upstream fractal layer; Semiconductor processing equipment.

11. 2. The semiconductor processing apparatus according to claim 1, At least three fractal layers are provided; Semiconductor processing equipment.

12. 2. The semiconductor processing apparatus according to claim 1, The body is formed from a ceramic material. Semiconductor processing equipment.

13. The semiconductor processing apparatus according to claim 12, the body being formed from a plurality of individual layers of ceramic material fused together; Semiconductor processing equipment.

14. The semiconductor processing apparatus according to claim 12, The body is a 3D printed structure. Semiconductor processing equipment.

15. The semiconductor processing apparatus according to any one of claims 1 to 14, a processing chamber; and further comprising a base, the pedestal is located within the processing chamber; the showerhead is positioned within the processing chamber above the pedestal. Semiconductor processing equipment.

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