Double air chamber fractal sprinkler

Abstract

A dual plenum fractal (DPF) showerhead is provided for distributing different semiconductor process gases across a semiconductor wafer during a processing operation. The DPF showerhead may have multiple layers, each having a pattern of gas distribution features, the gas distribution features on each layer having a shape that is substantially similar to the shape of the gas distribution features on its immediately upstream layer, but of smaller size. This "fractal"-like structure of the gas flow channels provides very uniform process gas delivery across the surface of the semiconductor wafer during a processing operation, thereby improving wafer uniformity.

Description

[0001] Incorporated by Reference

[0002] The PCT application form is filed concurrently with this specification as a part of this application. Each application to which this application claims the benefit or priority as identified in the concurrently filed PCT application form is incorporated herein by reference in its entirety and for all purposes. Background Art

[0003] Semiconductor manufacturing tools often include a "showerhead" for distributing semiconductor processing gases in a distributed manner over the semiconductor wafers being processed. These showerheads are typically characterized by a large open plenum space, e.g., a cylindrical volume within the showerhead sized to have a diameter at least as large as the diameter of the wafer being processed, which in turn is fluidly connected to a plurality of gas distribution ports on the underside of the showerhead. In some such tools, the showerhead may be configured to be able to distribute two different types of process gases over the wafer being processed.

[0004] A novel dual-gas showerhead design for use in semiconductor processing tools is disclosed herein. Summary of the invention

[0005] The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims.

[0006] In some embodiments, a semiconductor processing device is provided, which 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 also include a plurality of layers, the plurality of layers including a suitable subset of two or more fractal layers, each fractal layer including a group of first radially symmetric gas distribution features and a group of second radially symmetric gas distribution features. Each first radially symmetric gas distribution feature may include a first central plenum, a plurality of first spoke channels fluidly connected to and radiating outward from the first central plenum, and a plurality of first vertical pipe ports, each first vertical pipe port being located at a distal end of one of the first spoke channels. Each second radially symmetric gas distribution feature may include a second central plenum, a plurality of second spoke channels fluidly connected to and radiating outward from the second central plenum, and a plurality of second vertical pipe ports, each second vertical pipe port being located at a distal end of one of the second spoke channels. For each fractal layer of the fractal layer, each first radially symmetric gas distribution feature of the fractal layer can be positioned so that the corresponding first central air chamber is positioned below the first vertical pipe port of the adjacent upstream layer, and each second radially symmetric gas distribution feature of the fractal layer can be positioned so that the corresponding second central air chamber is positioned below the second vertical pipe port of the adjacent upstream layer.

[0007] In some embodiments, one of the fractal layers may also include a group of first partial radially symmetric gas distribution features, each of which has a first central gas-filled chamber having a smaller number of first spoke channels connected to its fluid than any of the first radially symmetric gas distribution features of the fractal layer.

[0008] In some further such embodiments, the body may also include a feed layer located immediately upstream of the fractal layer having the grouped first partial radially symmetric gas distribution characteristics. In such embodiments, the feed layer may include a plurality of first feed plenums, each first feed plenum having one or more first feed spoke channels fluidly connected thereto, each first feed spoke channel having a first feed riser port at its distal end, each first feed riser port being positioned above and fluidly connected to a corresponding one of the first central plenums in the fractal layer immediately downstream of the feed layer. In such embodiments, the first feed spoke channels having a first feed riser port fluidly connected to the first central plenum of the first radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer may each have a first length, and the first feed spoke channels having a first feed riser port fluidly connected to the first central plenum of the first partial radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer may each have a length longer than the first length.

[0009] In some further or alternative such embodiments, the fractal layer having the grouped first partial radially symmetric gas distribution features may also include a grouped second partial radially symmetric gas distribution features, each second partial radially symmetric gas distribution feature having a second central gas-filled chamber having a smaller number of second spoke channels than any of the second radially symmetric gas distribution features of the fractal layer.

[0010] In some such embodiments, the body may also include a feed layer immediately upstream of the fractal layer having the grouped first portion radially symmetric gas distribution characteristics and the grouped second portion radially symmetric gas distribution characteristics. In such embodiments, the feed layer may include a plurality of first feed plenums and a plurality of second feed plenums, each first feed plenum having one or more first feed spoke channels fluidly connected thereto, and each second feed plenum having one or more second feed spoke channels fluidly connected thereto, each first feed spoke channel having a first feed riser port at its distal end, and each second feed spoke channel having a second feed riser port at its distal end, each first feed riser port being positioned above and fluidically connected to a corresponding one of the first central plenums in the fractal layer immediately downstream of the feed layer, and each second feed riser port being positioned above and fluidically connected to a corresponding one of the second central plenums in the fractal layer immediately downstream of the feed layer. In such an embodiment, the first feed spoke channels of the first feed riser port having a first central plenum fluid connected to the first radially symmetric gas distribution characteristic in the fractal layer immediately downstream of the feed layer can each have a first length, the first feed spoke channels of the first feed riser port having a first central plenum fluid connected to the first portion of radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer can each have a length longer than the first length, the second feed spoke channels of the second feed riser port having a second central plenum fluid connected to the second portion of radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer can each have a second length, and the second feed spoke channels of the second feed riser port having a second central plenum fluid connected to the second portion of radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer can each have a length longer than the second length.

[0011] In some embodiments, the first radially symmetric gas distribution features of the fractal layer can each include four first spoke channels, and the second radially symmetric gas distribution features of the fractal layer can each include four second spoke channels.

[0012] In some further such embodiments, the first spoke channel and the second spoke channel of the first radially symmetric gas distribution feature and the second radially symmetric gas distribution feature of at least one fractal layer of the fractal layer may be at the same height, respectively.

[0013] In some additional or alternative such embodiments, each of the first spoke channels can be aligned with one of two orthogonal first channel axes, each of the second spoke channels can be aligned with one of two orthogonal second channel axes, and the first channel axis and the second channel axis are 45° out of phase (the first channel axis is at a 45° angle to the second channel axis).

[0014] In some further or alternative such embodiments, for each of the fractal layers having an immediately adjacent upstream fractal layer, the first radially symmetric gas distribution features of the fractal layer can 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 features of the immediately adjacent upstream fractal layer.

[0015] In some further or alternative such embodiments, for each of the fractal layers having an immediately adjacent upstream fractal layer, the second radially symmetric gas distribution features of the fractal layer can 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 features of the immediately adjacent upstream fractal layer.

[0016] In some embodiments, there may be at least three fractal layers.

[0017] In some embodiments, the body may be made of a ceramic material.

[0018] In some further such embodiments, the body may be made from multiple discrete layers of ceramic material fused together.

[0019] In some further or alternative such embodiments, the body may be a 3D printed structure.

[0020] In some embodiments, the apparatus may further include a processing chamber and a susceptor. In such embodiments, the susceptor may be positioned within the processing chamber, and the showerhead may be positioned above the susceptor within the processing chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various embodiments 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 refer to similar elements.

[0022] Figure 1 An isometric view of an exemplary dual-plenum fractal showerhead is depicted.

[0023] Figure 2 Depicted Figure 1Reverse isometric view of an exemplary dual plenum fractal showerhead.

[0024] Figure 3 and Figure 4 Depicted separately Figure 1 Top and bottom views of an exemplary dual-plenum fractal showerhead.

[0025] Figure 5 Depicted Figure 1 Isometric exploded view of an exemplary dual-plenum fractal showerhead.

[0026] Figure 6 A detail view of an exemplary first radially symmetric gas distribution feature is depicted.

[0027] Figure 7 A detail view of an exemplary first radially symmetric gas distribution feature is depicted.

[0028] Figure 8 Depicted are size comparisons between sets of radially symmetric gas distribution features from each of the three different fractal layers.

[0029] Fig. 9 Provides an observation diagram on the relative proportions of gas distribution features from different fractal layers.

[0030] Figures 10 to 15 Shows Figure 1 Plan views of the various layers of an exemplary dual-plenum fractal showerhead.

[0031] Fig.16 Depicted Figure 1 An isometric view of the plenum volumes within an exemplary dual-plenum fractal showerhead.

[0032] Fig.17 Depicted Figure 1 An isometric view of the volume of another plenum chamber within an exemplary dual-plenum fractal showerhead.

[0033] Fig.18 Depicted Figure 1 An isometric view of the volumes of the two plenum chambers within an exemplary dual-plenum fractal showerhead.

[0034] Fig.19 A schematic diagram of a semiconductor processing chamber having a showerhead as described herein is depicted.

[0035] Figure 1-18 The figures are drawn to scale in each drawing, but the scales may vary between the figures. The figures depict only examples of the concepts discussed herein, and it will be readily appreciated that the concepts discussed herein may be implemented in numerous alternative embodiments, all of which are considered to fall within the scope of the present invention. DETAILED DESCRIPTION

[0036] Importantly, the concepts discussed herein are not limited to any single aspect or embodiment discussed herein, nor to any combination and / or arrangement of such aspects and / or embodiments. In addition, each aspect and / or embodiment of the present invention may be employed alone or in combination with one or more of the other aspects and / or embodiments thereof. For the sake of brevity, many of these arrangements and combinations will not be discussed and / or described separately herein.

[0037] The dual plenum fractal nozzles discussed herein can be configured to evenly distribute process gas to a processing volume above a semiconductor wafer in a semiconductor processing chamber. These dual plenum fractal (DPF) nozzles can provide a variety of benefits compared to more traditional dual plenum nozzles. For example, since there are no large plenums, such as plenums that are roughly circular in shape and span the entire area where the gas distribution holes of the nozzle are located, the amount of process gas that must be directed into the nozzle to deliver the process gas through the gas distribution port of the nozzle can be greatly reduced in the DPF nozzle design discussed herein compared to conventional open plenum volume nozzles. Another benefit is that for a given plenum of a DPF nozzle, the fractal characteristics of the various flow paths in the DPF nozzle make the flow paths leading to each gas distribution port have equal or at least very similar flow resistances, thereby reducing or eliminating the variation in the time it takes for the gas introduced into the plenum through the air inlet to reach any given gas distribution port of the plenum. For example, the gas flowing through the plenum of a fractal nozzle may generally experience substantially the same fluid flow path characteristics regardless of which gas distribution port it ultimately flows to, e.g., after the gas reaches the fractal layers of such a nozzle (these layers will be described in detail later below), the gas may flow through a continuous gas flow channel having channel segments of the same course, and the channel segments have similar lengths, cross-sectional shapes, and areas. This may help promote more uniform wafer processing because the entire wafer surface will be exposed to the process gas at approximately the same time, as opposed to, for example, a nozzle where the process gas flows out of the center of the nozzle for a period of time before flowing out of the periphery of the nozzle. Another benefit of the DPF nozzle discussed herein is that it can be made of a variety of materials, including metals (stainless steel, aluminum, etc.) and ceramics (aluminum oxide, silicon oxide, etc.).

[0038] In general, a DPF nozzle, such as those discussed herein, may have two patterns of gas distribution holes on the bottom side of the nozzle, one for each plenum. In the DPF example discussed below, the two patterns are generally square patterns that are 45° out of phase with each other (and which omit several instances of gas distribution holes at the corners of each square pattern, e.g., a 4×4 sub-pattern of gas distribution holes is omitted at each corner of each pattern). The 45° out of phase arrangements may be used in an internal layout for various channels that partially define the two gas distribution plenums within the exemplary DPF nozzle. This enables very dense packing of gas flow channels within the DPF nozzle and reduces the gas distribution hole spacing, thereby enabling a finer-grained distribution of the process gas across the semiconductor wafer.

[0039] The DPF nozzle can be used in both asynchronous (i.e., the process gas flows alternately through each plenum at different times) and synchronous (i.e., the process gas flows through both plenums simultaneously). In some additional examples, the DPF nozzle can be used in a mixed manner, wherein one plenum has a process gas flowing continuously through it, while the other plenum has two or more different gases flowing through it in an alternating or cyclic manner. In the former case, it can be applied, for example, to atomic layer deposition or other alternating process gas application processes. Compared to conventional nozzles, the reduced volume of the DPF nozzle can allow a reduced delay time before the desired amount of process gas is delivered to the wafer, thereby reducing the total duration of each gas injection cycle (thereby reducing the processing time / increasing the yield). In the latter case, it can be applied, for example, to a processing operation in which two process gases flow simultaneously into the processing space above the semiconductor wafer so that they react to achieve a desired processing effect on the wafer. Improving the simultaneity performance of the DPF nozzle can reduce the chance that one reactant is present in the wafer processing space but the other is not present. In particular, the DPF nozzles discussed herein may be used in methods such as those discussed in U.S. Patent Application No. 62 / 767,198 (filed on November 14, 2018, entitled “METHODS FORMAKING HARD MASKS USEFUL IN NEXT-GENERATION LITHOGRAPHY”) and U.S. Patent Application No. 62 / 868,710 (filed on June 28, 2019, entitled “EUV PHOTORESIST WITH MULTIPLE EUV-ABSORBING ELEMENTS AND VERTICAL COMPOSITION GRADIENT”), both of which are incorporated herein by reference in their entirety.

[0040] Figure 1 depicts an isometric view of an exemplary dual plenum fractal (DPF) spray head; Figure 2 Depicted Figure 1A reverse isometric view of an exemplary DPF nozzle of FIG. Figure 3 and Figure 4 Depicted with Figure 1 Top and bottom views of the same exemplary DPF spray head.

[0041] In appearance, Figure 1 The DPF nozzle 100 of FIG. 1 is slightly different from many other dual plenum nozzles—it is generally circular in shape, has a plurality of inlets on the top surface, such as the first plenum inlet 102 and in this example a plurality of (four) second plenum inlets 104, and two hole patterns on its bottom surface, such as the first hole pattern 112 and the second hole pattern 114 of gas distribution holes (such as the first gas distribution holes 106 and the second gas distribution holes 108). It should be noted that both the first hole pattern 112 and the second hole pattern 114 are in the form of generally rectangular (or more accurately, square) arrays, but the two rectangular arrays are positioned 45° out of phase with each other. There is also an additional first gas distribution hole 106 that is not part of the rectangular first hole pattern 112—the additional first gas distribution hole 106 is located at the center of the DPF nozzle 100. In most conventional showerheads, the hole pattern of the gas distribution holes is typically confined to have a generally circular outer extent, i.e., the hole patterns extend outward to a circular boundary, and all of the gas distribution holes for a given plenum are located within the circular boundary and are generally uniformly distributed within the boundary. However, in the exemplary DPF showerhead, this is not the case (but may be the case, as discussed further below). It can be seen that the first gas distribution holes 106 and the second gas distribution holes 108 are generally uniformly distributed within the circular wafer overlap region 110 (in this example, the size of the wafer overlap region 110 is designed to be the same size as the semiconductor processing wafer (which is typically positioned below the DPF showerhead during processing), such as 300 mm in diameter (but in some embodiments, such uniform hole distribution can be maintained, for example, over an entire or even larger diameter circular area, such as to provide uniform gas distribution during processing to or beyond the wafer periphery). However, both the first hole pattern 112 and the second hole pattern 114 have a portion extending beyond the wafer overlap region 110. Located at the wafer overlap region 110, the first and second hole patterns 112 and 114 are generally uniformly distributed within the wafer overlap region 110. The first gas distribution holes 106 and the second gas distribution holes 108 outside the overlap region 110 are no longer evenly distributed relative to each other. As will be seen in the following discussion, in the exemplary DPF nozzle, gas distribution ports located outside the wafer overlap region 110 are included to allow the various gas distribution features for each plenum in the various layers within the DPF nozzle to have the same design for each layer; it should be understood that with appropriate modifications (for example, by using gas distribution features of varying designs in such layers near the periphery of the DPF nozzle 100), a DPF nozzle can be provided that reduces or eliminates gas distribution ports located outside the wafer overlap region 110. Such alternative embodiments are considered to be within the scope of the present invention.

[0042] It will be observed that in the exemplary embodiment, the array pitches d1 and d2 of the first hole pattern 112 and the second hole pattern 114 are respectively 106 , 108 , 106 ... In the present exemplary DPF nozzle, the first gas distribution holes 106 and the second gas distribution holes 108 have the same diameter, resulting in that when the process gas is directed to the respective inlets and the same inlet pressure is maintained (assuming that both plenums have subsonic flow conditions; in actual practice of some embodiments, a control system with a mass flow controller may be used to ensure that the same mass flow rate of gas is delivered through each plenum, which may result in each plenum experiencing a different inlet pressure and a different exit velocity from its corresponding gas distribution port), the amount of process gas flowing through the second gas distribution holes 108 is approximately twice the amount of process gas flowing through the first gas distribution holes 106. However, in other embodiments, the diameter of one or both of the first gas distribution holes 106 and the second gas distribution holes 108 may be varied, such that the first gas distribution holes 106 are larger or smaller than the second gas distribution holes, to adjust the potential flow rate of gas flowing through the two sets of gas distribution holes.

[0043] Figure 5 Depicted Figure 1 An isometric exploded view of an exemplary DPF nozzle. As can be seen from the exploded view, the DPF nozzle 100 can be divided into a plurality of different layers 116, each of which has different gas distribution characteristics. It should be understood that such a DPF nozzle 100 can be formed, for example, by machining each layer into discrete components or otherwise forming each layer into discrete components, and then joining or fusing the various layers together to form a laminated stack to provide the DPF nozzle. However, in other embodiments, other techniques may be used or equivalent structures may be produced, for example, additive manufacturing may be used to "3D print" a DPF nozzle structure, for example, from metal, ceramic or other materials.

[0044] In this discussion, reference to a layer “upstream” of a particular layer should be understood as the one that is closer to the “top” of the DPF nozzle 100 (e.g., closer to the first plenum inlet 102 or the second plenum inlet 104); reference to a layer “downstream” of a particular layer will be understood as the one that is closer to the “bottom” of the DPF nozzle 100 (e.g., closer to the first gas distribution hole 106 or the second gas distribution hole 108). Reference to a layer “immediately upstream” of a particular layer refers to the upstream layer closest to that layer. Reference to a layer “immediately downstream” of a particular layer similarly refers to the downstream layer closest to that layer. It should also be understood that although one may arbitrarily divide any given nozzle into layers in any manner one deems appropriate, the use of “layer” in this application should be understood to refer to, for example Figure 5 The layers depicted, for example, wherein each layer has standpipe holes (or gas distribution holes) on one side and a gas flow channel / plenum on the other side, and each standpipe port / gas distribution hole in the layer terminates in one of the gas flow channels (the inlet layer may be an exception, which only has standpipe holes passing through it in the form of a first plenum inlet 102 and a second plenum inlet 104).

[0045] The various layers 116 may include, for example, an inlet layer 118 (including layer 116a), a feed layer 120 (for example, including layers 116b and 116c), and a fractal layer 122 (for example, including layers 116d, 116e, and 116f). The inlet layer 118 may include, for example, through-holes or other features through which the process gas may be introduced into the plenum of the DPF nozzle 100, such as the first plenum inlet 102 and the second plenum inlet 104.

[0046] The feed layer 120 may include, for example, layer 116b, which includes a first feed channel 124 and a second feed channel 126, which may each fluidly connect one of the corresponding first plenum inlet 102 or the second plenum inlet 104 with a corresponding first feed riser port 138 or a second feed riser port 140 within layer 116b. The first feed riser port 138 and the second feed riser port 140 in layer 116b may pass through the bottom of layer 116b and may each fluidly connect one of the corresponding first feed channel 124 or the second feed channel 126 with a corresponding first feed plenum 130 or a second feed plenum 132 in layer 116c.

[0047] Layer 116c, which is one of the feed layers 120, may have a plurality of gas distribution features, each of which generally takes the form of a central plenum having a plurality of feed spoke channels extending outwardly therefrom. For example, layer 116c may have a plurality of first feed plenums 130 (four are shown, but other numbers may be used—generally there are as many first feed riser ports 138 in the immediately upstream layer 116). Similarly, layer 116c may also have a plurality of second feed plenums 132 (four are shown, but other numbers may be used—generally there are as many second feed riser ports 140 in the immediately upstream layer 116).

[0048] Each first feed plenum 130 may have a plurality of first feed spoke channels 134 radiating outwardly from the first feed plenum 130; each first feed spoke channel 134 may terminate at a corresponding first feed riser port 138 in layer 116c, which leads to an immediately downstream layer 116, such as layer 116d. Similarly, each second feed plenum 132 may have a plurality of second feed spoke channels 136 radiating outwardly from the second feed plenum 132; each second feed spoke channel 136 may terminate at a corresponding second feed riser port 140 in layer 116c, which leads to an immediately downstream layer 116. Each first feed riser port 138 and second feed riser port 140 in layer 116c may be positioned approximately centered above the corresponding plenum feature in the immediately downstream layer.

[0049] It should be noted that the feed spoke channels radiating outward from each feed plenum do not necessarily have equal flow resistance due to the variation in the geometry of the feed spoke channels. This will be discussed in more detail later.

[0050] It should also be noted that Figure 5 The feed channel and feed spoke channel shown in each also include two internal support walls 128, which generally extend from one end of these channels to the other end along the length of such channels. Such support walls 128 (or other structures, for example) may be optionally included in some embodiments. For example, if the DPF nozzle 100 is made of green embryo machined ceramic layers (which are stacked together and then fired in a kiln to form a single melt-hardened ceramic component), it may be desirable for the wider channel to include one or more internal support walls 128 (or other support structures) to provide mechanical support for the layer forming the "top" of such channels. Other geometries and / or other manufacturing techniques may not require such support walls 128.

[0051] After flowing through the feed layer 120, the process gas is then directed into the fractal layer 122. The fractal layers 122 are typically each characterized by the same repeating radially symmetric gas distribution feature (or portion thereof) for each plenum, with the radially symmetric gas distribution feature of each layer immediately downstream of the layer being a scaled-down version of the corresponding radially symmetric gas distribution feature in that layer. In this example, the overall size of each radially symmetric gas distribution feature in the layer is scaled down by approximately 50% relative to the corresponding radially symmetric gas distribution feature in the immediately upstream layer, but other embodiments may utilize different scaling ratios. Figure 8 Depicted Figure 5 1 and 2 - a comparison of the sizes of the radially symmetric gas distribution feature groups for each of the three fractal layers 122 shown in FIG. 1 - each radially symmetric gas distribution feature group is shown in proportion to the other radially symmetric gas distribution feature groups shown. As can be seen from the dashed-dotted-dashed lines through the centers of the selected standpipe ports of each radially symmetric gas distribution feature group, in each fractal layer 122, the center-to-center standpipe hole spacing of each radially symmetric gas distribution feature group is reduced by 50% compared to the immediately upstream radially symmetric gas distribution feature group.

[0052] This characteristic gives the gas distribution channels of each plenum in the DPF nozzle a "fractal" appearance, thus giving meaning to the name "dual plenum fractal nozzle". It should be noted that in some embodiments, specific sub-features in each radially symmetric gas distribution feature may be scaled up or down relative to corresponding features of the radially symmetric gas distribution feature in the immediately upstream layer. For example, in the exemplary DPF nozzle 100, the center-to-center distance between the riser ports of a given radially symmetric gas distribution feature is 50% of the corresponding center-to-center distance between the riser ports of the radially symmetric gas distribution feature immediately upstream of the given radially symmetric gas distribution feature. However, the cross-sectional width of each spoke channel may actually be increased relative to the center-to-center spacing in the radially symmetric gas distribution feature immediately upstream. Fig. 9 Provides additional observations about this feature. Fig. 9, three sets of one first radially symmetric gas distribution feature 146 and four adjacent second radially symmetric gas distribution features 148 (one set for each of the three fractal layers 122) have been scaled so that their corresponding standpipe holes all have the same center-to-center distance between them and then stacked so that they are centered about each other. It can be seen that the first and second radially symmetric gas distribution features 146' and 148' (shown in dotted outline) from layer 116e have spoke channels that are slightly wider (relative to the center-to-center distance between the standpipe holes) than the corresponding first and second radially symmetric gas distribution features 146 and 148, respectively. Similarly, the first and second radially symmetric gas distribution features 146" and 148" (shown in dashed outline) from layer 116f have spoke channels that are slightly wider (relative to the center-to-center distance between the standpipe holes) than the corresponding first and second radially symmetric gas distribution features 146' and 148'.

[0053] Additionally, it can be seen that the diameters of the first and second standpipe apertures of each radially symmetric gas distribution feature relative to the center-to-center spacing may vary between radially symmetric gas distribution features in a fractal layer that are immediately upstream / downstream of each other.

[0054] In some embodiments, a portion of the radially symmetric gas distribution feature of one or more fractal layers 122 may be provided in only a "partial form", i.e., with only a portion of the radially symmetric gas distribution feature. For example, the radially symmetric gas distribution feature in the exemplary DPF nozzle is a +-shaped or an X-shaped, each of which has four spoke channels radiating outward from a central plenum. A partial radially symmetric gas distribution feature in this case may be constructed similarly, but lacking one or two spoke channels.

[0055] For example, in layer 116d, there are a plurality of first radially symmetric gas features 146 and a plurality of second radially symmetric gas features 148, each of which is in the shape of a + or an X (note, however, that first radially symmetric gas features 146 are larger than second radially symmetric gas features 148—see earlier discussion regarding array spacing). First radially symmetric gas features 146 and second radially symmetric gas features 148 each have a corresponding central plenum and a plurality of spoke channels radiating outward therefrom.

[0056] Figure 6 An exemplary first radially symmetric gas distribution feature 146 is depicted, and Figure 7 An exemplary second radially symmetric gas distribution feature 148 is depicted; Figure 6 and 714 and 15. The first radially symmetric gas distribution feature 146 is shown to the same scale. It can be seen that the first radially symmetric gas distribution feature 146 has a first central plenum 158, which can be positioned directly below and fluidly connected to a corresponding first standpipe port 162' (or, in some examples, a first feed standpipe port 138) of the immediately upstream layer 116. The first central plenum 158 can have a plurality (four in this example) of first spoke channels 154 radiating outwardly from the first central plenum 158 in a radially symmetric manner. Each first spoke channel 154 can terminate at a corresponding first standpipe port 162 (or, in the case of the most downstream layer 116, at a corresponding first gas distribution hole 106).

[0057] Similarly, Figure 7 The second radially symmetric gas distribution feature 148 has a second central plenum 160 that can be positioned immediately below and fluidly connected to a corresponding second standpipe port 164' (or, in some examples, a second feed standpipe port 140) of the upstream layer 116. The second central plenum 160 can have a plurality (four in this example) of second spoke channels 156 radiating outwardly from the second central plenum 160 in a radially symmetric manner. Each second spoke channel 156 can terminate at a corresponding second standpipe port 164 (or, in the case of the most downstream layer 116, at a corresponding second gas distribution hole 108).

[0058] return Figure 5 , it should be noted that the first radially symmetric gas distribution feature 146 and the second radially symmetric gas distribution feature 148 occupy approximately the central region of layer 116d, but near the periphery of layer 116d, the first partial radially symmetric gas distribution feature 142 and the second partial radially symmetric gas distribution feature 144 are used. The first partial radially symmetric gas distribution features 142 each have only two first spoke channels 154, and the second partial radially symmetric gas distribution features 144 each have only three second spoke channels 156. The remaining fractal layers 122 in this example have only radially symmetric gas distribution features and do not have any partial radially symmetric gas distribution features, but other embodiments may include partial radially symmetric gas distribution features in other fractal layers 122.

[0059] While the previous figures clearly convey the structure of the exemplary DPF nozzle 100, further figures are provided. Figures 10 to 15 To display Figure 1 Although these figures are somewhat redundant with the previous figures, they provide additional clarity and may be particularly referenced in the following discussion.

[0060] Unless certain mitigating measures are taken, the use of a partially radially symmetric gas distribution feature may result in a flow imbalance in the DPF nozzle, as shown. For example, with respect to a corresponding partially radially symmetric gas distribution feature, if the same amount of process gas is provided to each central plenum of the radially symmetric gas distribution feature at the same gas flow rate, the standpipe ports of the partially radially symmetric gas distribution feature will each exhibit an increased gas flow rate compared to the standpipe ports of the radially symmetric gas distribution feature - this is due to the fact that the partial radially symmetric gas distribution feature has fewer spoke channels and corresponding standpipe ports than the radially symmetric gas distribution feature. Therefore, the standpipe ports of the partially radially symmetric gas distribution feature have a smaller total cross-sectional area than the standpipe ports of the radially symmetric gas distribution feature, resulting in more gas volume flowing through each standpipe port of the partially radially symmetric gas distribution feature than through each standpipe port of the radially symmetric gas distribution feature. This is not desirable because it will result in downstream radially symmetric gas distribution features in subsequent layers 116 provided with gas by the partially radially symmetric gas distribution feature receiving a disproportionate amount of gas (compared to the radially symmetric gas distribution features in those same downstream layers provided with gas by the radially symmetric gas distribution features). This in turn will eventually lead to uneven gas delivery through the gas distribution holes.

[0061] To mitigate or prevent this effect, the feed channel that provides the process gas from the feed standpipe port to the radially symmetric gas distribution feature immediately downstream can be designed to have a longer length than the feed channel that provides the process gas from the feed standpipe port to the radially symmetric gas distribution feature immediately downstream. Fig.12 It can be seen that the lengths of two of the three first feed spoke channels 134 radiating outward from each first feed air chamber 130 are approximately twice the lengths of the remaining first feed spoke channels 134 radiating outward from each first feed air chamber 130; this increased length increases the flow resistance of these first feed spoke channels 134, thereby causing the flow rate experienced by the first feed vertical pipe ports 138 located at the ends of these first feed spoke channels 134 to be approximately half of that of the first feed vertical pipe ports 138 of the remaining first feed spoke channels 134 radiating outward from each first feed air chamber 130. Similarly, one of the four second feed spoke channels 136 radiating outward from each second feed plenum 132 has an increased length compared to the other second feed spoke channels 136 radiating outward therefrom; this has a similar effect and can cause a portion of the radially symmetric gas distribution feature on the immediately downstream layer having only three spokes to experience reduced fluid flow, thereby promoting gas flow uniformity outside the DPF nozzle 100.

[0062] After the gas reaches each gas distribution feature, the gas flow can be roughly evenly distributed among the various spoke channels before passing to the next set of gas distribution features (or outflow gas distribution ports) in the immediately downstream layer; this recursive splitting feature can evenly distribute the process gas throughout the wide area of ​​the showerhead. In this example, there are three fractal layers 122, but more or fewer such layers can be used depending on how finely or coarsely the gas is to be distributed.

[0063] In the exemplary DPF nozzle 100, it can be seen that for each plenum, the radially symmetric gas distribution feature in a given fractal layer 122 has spoke channels aligned with channel axes that are 45° out of phase with each other. Figure 5 In the fractal layer 116d, the first radially symmetric gas distribution feature 146 has a first spoke channel 154 aligned with the first channel axis 150, and the second radially symmetric gas distribution feature 148 has a second spoke channel 156 aligned with the second channel axis 152; it can be seen that the phases of the first channel axis 150 and the second channel axis 152D differ by 45° from each other.

[0064] Fig.16 Depicted Figure 1 An isometric view of an abstraction of the plenum volumes within an exemplary dual-plenum fractal showerhead. Fig.17 Depicted Figure 1 An abstracted isometric view of the volume of another plenum chamber in an exemplary dual-plenum fractal showerhead. Fig.18 Depicted Figure 1 An isometric view of an abstraction of the volumes of the two plenum chambers in an exemplary dual-plenum fractal showerhead.

[0065] exist Figures 16 to 18, it can be easily seen that each radially symmetric gas distribution feature or part of a radially symmetric gas distribution feature in a fractal layer has a central plenum that is fluidly connected to a standpipe port at the far end of one of the spoke channels radiating outward from the central plenum of a radially symmetric gas distribution feature in an immediately upstream fractal layer (or to a feed standpipe port of one of the feed layers 120). Since the radial spoke channels of each plenum in each layer are arranged at a phase difference of 45°, it is also possible to achieve a very high gas distribution hole density on the bottom surface of the DPF nozzle, and any gas distribution port from the inlet to any plenum can still achieve approximately equal flow resistance. For example, this configuration allows each of the individual second spoke channels 156 to extend partially into the space between two adjacent first spoke channels 154, thereby allowing each of the associated second riser ports 164 (or second gas distribution holes 108 in layer 116f) to be located at an intermediate position along a line between the two first riser ports 162 (or first gas distribution holes 106) closest to the second riser ports.

[0066] It should also be noted that in the exemplary DPF nozzle, many of the gas distribution holes and / or radially symmetric gas distribution features are located outside the wafer overlap region 110, and thus will provide process gas that may generally never actually hit the wafer because the process gas delivered from the radially symmetric gas distribution features and / or gas distribution holes within the wafer overlap region 110 tends to push such process gas outward and away from the wafer. Thus, the process gas delivered from the gas distribution holes outside the wafer overlap region 110 may essentially be considered excess or wasted process gas. As described above, in some embodiments, 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 nozzle. However, doing so may require extensive customization of a variety of radially symmetric gas distribution features (indeed, they may no longer reasonably be considered "radially symmetric gas distribution features") to ensure that the gas flow through the gas distribution holes remains uniform. By including radially symmetric gas distribution features and / or gas distribution holes outside of the wafer overlap region 110, the split flow occurring at each radially symmetric gas distribution feature remains the same for all radially symmetric gas distribution features in the fractal layer, thereby producing a uniform flow through the gas distribution holes of each plenum without requiring complex modifications to the radially symmetric gas distribution features in the fractal layer 122. It is also noted that as the overall size of the radially symmetric gas distribution features shrinks, they may become increasingly susceptible to small size changes, making it increasingly difficult to fine-tune the gas flow characteristics of each radially symmetric gas distribution feature individually through customization. Therefore, although the method shown with respect to the exemplary DPF nozzle 100 may result in some excess or waste of gas, the resulting process gas distribution across the wafer is substantially uniform without requiring custom modifications to the radially symmetric gas distribution features in the fractal layer.

[0067] As previously described, there is a gas distribution hole on the underside of the DPF nozzle 100 that is not part of any hole pattern - the center hole. Such a center hole may optionally be included to promote additional wafer processing uniformity and may be connected to, for example, the first plenum inlet fluid. Depending on the specific processing conditions required, it may be necessary to design the size of the center hole to be the same size as the other gas distribution holes of the first plenum, or alternatively larger or smaller than the other gas distribution holes. In embodiments where a center hole is used and its size is the same as the other first gas distribution holes, the flow rate through the center hole can be modified in some such embodiments by changing the flow path resistance from the first inlet through the nozzle to the center hole; it does not necessarily have to have the same flow resistance as the other first gas distribution holes of the first plenum.

[0068] It should be further noted that although the present invention is primarily directed to a dual-plenum fractal spray head, similar principles can be implemented in a single-plenum fractal spray head form, for example, by simply omitting one of the plenums and related features. Such a single-plenum fractal (SPF) spray head is also considered to fall within the scope of the present invention.

[0069] DPF (and SPF) showerheads according to the concepts discussed herein may be used in semiconductor processing operations as previously discussed. For example, a DPF or SPF showerhead may be used in a semiconductor processing chamber (e.g., Fig.19 Such a DPF or SPF showerhead 100 may be suspended in the chamber 170 by a rod 176, which may include a gas supply passage for delivering a process gas to the inlet of the DPF or SPF showerhead for distribution over a wafer 174, which may be supported in the chamber 170 by a susceptor 172.

[0070] In some embodiments, a controller may be provided. The controller may be part of a system (which may include the above examples) and may be operably connected to various valves, mass flow controllers, pumps, etc., to be able to receive information from such equipment and / or control such equipment. Such a system may include semiconductor processing equipment, which includes one or more processing tools, one or more chambers, one or more platforms for processing, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems may be integrated with electronic devices for controlling their operations before, during, and after the processing of semiconductor wafers or substrates. Electronic devices may be referred to as "controllers", which may control various components or subcomponents of one or more systems. Depending on the processing requirements and / or system type, the controller may be programmed to control any of the processes disclosed herein, including controlling the delivery of various processing gases (e.g., delivered to the DPF or SPF nozzles described herein), temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, flow rate settings, fluid delivery settings, and position and operation settings.

[0071] In general, a controller can be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. The integrated circuit can include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and / or one or more microprocessors, or a microcontroller that executes program instructions (e.g., software). The program instructions can be instructions sent to the controller in the form of various individual settings (or program files) that define operating parameters for performing specific processing on or for a semiconductor wafer or system. In some embodiments, the operating parameters can be part of a recipe defined by a process engineer to complete one or more processing steps during the manufacture of one or more (kinds of) layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0072] In some embodiments, the controller can be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system or a combination thereof. For example, the controller can be in the "cloud" or all or part of a wafer factory (fab) host system, which can allow remote access to wafer processing. The computer can implement remote access to the system to monitor the current progress of manufacturing operations, check the history of past manufacturing operations, check the trends or performance standards of multiple manufacturing operations, change the parameters of the current processing, set the processing steps to follow the current processing, or start a new processing. In some examples, a remote computer (such as a server) can provide a processing recipe to the system through a network (which can include a local network or the Internet). The remote computer can include a user interface that enables input or programming of parameters and / or settings, and then the parameters and / or settings are sent from the remote computer to the system. In some examples, the controller receives instructions in the form of data, which specifies the parameters of each processing step to be performed during one or more operations. It should be understood that the parameters can be specific to the type of processing to be performed and the type of tool, and the controller is configured to interface with the tool or control the tool. Thus, as described above, the controller may be distributed, for example, by including one or more discrete controllers networked together and working toward a common purpose (e.g., processing and control as described herein). An example of a distributed controller for such a purpose is one or more integrated circuits on a chamber that communicate with one or more integrated circuits remotely (e.g., at a platform level or as part of a remote computer), which combine to control processing on the chamber.

[0073] Example systems may include, but are not limited to, plasma etch chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, chamfer edge etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the manufacture and / or preparation of semiconductor wafers.

[0074] As described above, depending on one or more processing steps to be performed by the tool, the controller can communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, a host computer, another controller, or tools used in material transport to transport wafer containers to and from tool locations and / or load ports in a semiconductor manufacturing facility.

[0075] For purposes of the present invention, the term "fluidic connection" is used with respect to volumes, plenums, holes, etc. that can be connected to each other to form a fluid connection, similar to the way the term "electrical connection" is used with respect to components that are connected together to form an electrical connection. If the term "fluid interposition" is used, it can be used to refer to a component, volume, plenum, or hole that is fluidly connected to at least two other components, volumes, plenums, or holes, so that fluid flowing from one of these other components, volumes, plenums, or holes to another of these other components, volumes, plenums, or holes flows through the "fluid interposition" component before reaching the other of these components, volumes, plenums, or holes. For example, if a pump is fluidly interposed between a container and an outlet, fluid flowing from the container to the outlet will flow through the pump before reaching the outlet.

[0076] It is further understood that the generic term "standpipe port" may be used herein to refer not only to the standpipe port of each radially symmetrical gas distribution feature, but may also be used herein to refer to the feed standpipe port and the gas distribution hole. Thus, for example, the gas distribution hole may be described not only as a gas distribution hole, but also as a standpipe port. Similarly, the feed standpipe port may also be referred to simply as a standpipe port. In general, the standpipe port on the lowermost surface of a DPF or SPF nozzle (when the nozzle is installed in a process chamber) may also be referred to as a "gas distribution hole".

[0077] It should be understood that, for example, the phrase "for each <item> of the one or more <items>" or "each <item> of the one or more <items>" (if used herein) is to include both single item groups and multiple item groups, i.e., the use of the phrase "for ... each" means that it is used in a programming language to refer to each item in the entire group of items being referred to. For example, if the group of items being referred to is a single item, then "each" will only refer to that single item (despite the fact that the dictionary definition of "each" is often defined to mean "each of two or more things"), and does not mean that there must be at least two of those items.

[0078] It should also be understood that the "layer" referred to in this disclosure may refer to a physically separable layer (e.g., a layer in a laminated structure that is then bonded, fused, or otherwise fixed in place relative to another layer in the laminated structure), or more generally to an area of ​​a structure that is bonded between two reference surfaces; such a structure may be composed of multiple parts that are assembled or bonded together, or in some instances may be a unitary structure (e.g., a single-piece structure). For example, a cast or additively manufactured single-piece part may still be considered to have features on its different "layers" even if the part is not actually built by bonding physically separate layers together (although it can be said that most additively manufactured parts inherently have a layer structure because they are typically printed one thin layer at a time). It should also be understood that the "layer" of a part that is actually manufactured as a laminate (i.e., from discrete layers) is not necessarily aligned with one of these discrete layers. For example, a layer of a part may be defined as including only a portion of such discrete layer part, a portion of two adjacent discrete layer parts, or a portion of one or two non-adjacent discrete layer parts and a discrete layer part therebetween.

Claims

1. A semiconductor processing device comprising: A nozzle, the nozzle comprising: main body; The first plenum chamber entrance; The entrance to the second plenum chamber; a plurality of first gas distribution holes; and A plurality of second gas distribution holes, wherein: The body includes a plurality of layers, the plurality of layers including a subset of two or more fractal layers, each fractal layer including a set of first radially symmetric gas distribution features and a set of second radially symmetric gas distribution features, each first radially symmetric gas distribution feature comprises a first central plenum, a plurality of first spoke channels fluidly connected to and radiating outwardly from the first central plenum, and a plurality of first standpipe ports, each first standpipe port being located at a distal end of one of the first spoke channels, each second radially symmetric gas distribution feature comprises a second central plenum, a plurality of second spoke channels fluidly connected to and radiating outwardly from the second central plenum, and a plurality of second standpipe ports, each second standpipe port being located at a distal end of one of the second spoke channels, The first radially symmetric gas distribution feature and the second radially symmetric gas distribution feature are fluidly isolated from each other within the body, For each fractal layer of the fractal layer: each first radially symmetric gas distribution feature of the fractal layer is positioned such that the corresponding first central plenum is positioned immediately below a first standpipe port of an upstream layer, and Each second radially symmetric gas distribution feature of the fractal layer is positioned such that the corresponding second central plenum is positioned below a second standpipe port of the immediately upstream layer.

2. The semiconductor processing apparatus according to claim 1, wherein: One of the fractal layers also includes a group of first partially radially symmetric gas distribution features, each of which has a first central plenum having a smaller number of first spoke channels fluidly connected thereto than any of the first radially symmetric gas distribution features of the fractal layer.

3. The semiconductor processing apparatus of claim 2, wherein the body further comprises a feed layer located immediately upstream of the fractal layer having the set first partial radially symmetric gas distribution characteristics, wherein: the feed layer comprising a plurality of first feed plenums, each first feed plenum having one or more first feed spoke channels fluidly connected thereto, each first feed spoke channel having a first feed riser port at a distal end thereof, each first feed riser port being positioned above and fluidly connected to a corresponding one of the first central plenums in the fractal layer immediately downstream of the feed layer, the first feed spoke channels having first feed standpipe ports fluidly connected to a first central plenum of the first radially symmetric gas distribution feature in the fractal layer immediately downstream of the feed layer each having a first length, and The first feed spoke channels having first feed standpipe ports fluidly connected to a first central plenum of the first partial radially symmetric gas distribution feature in the fractal layer immediately downstream of the feed layer each have a length greater than the first length.

4. The semiconductor processing equipment according to claim 2, wherein: The fractal layer having the grouped first partial radially symmetric gas distribution features also includes a grouped second partial radially symmetric gas distribution features, each second partial radially symmetric gas distribution feature having a second central gas-filled chamber having a smaller number of second spoke channels than any of the second radially symmetric gas distribution features of the fractal layer.

5. The semiconductor processing apparatus of claim 4, wherein the body further comprises a feed layer immediately upstream of the fractal layer having the set of first partial radially symmetric gas distribution features and the set of second partial radially symmetric gas distribution features, wherein: The feed layer includes a plurality of first feed plenums and a plurality of second feed plenums, each first feed plenum having one or more first feed spoke channels fluidly connected thereto, and each second feed plenum having one or more second feed spoke channels fluidly connected thereto, each first feed spoke channel having a first feed riser port at a distal end thereof, and each second feed spoke channel having a second feed riser port at a distal end thereof, each first feed riser port being positioned above and fluidly connected to a corresponding one of the first central plenums in the fractal layer immediately downstream of the feed layer, and each second feed riser port being positioned above and fluidly connected to a corresponding one of the second central plenums in the fractal layer immediately downstream of the feed layer, the first feed spoke channels having first feed riser ports fluidly connected to a first central plenum of the first radially symmetric gas distribution feature in the fractal layer immediately downstream of the feed layer each having a first length, the first feed spoke passages having first feed riser ports fluidly connected to a first central plenum fluidly connected to the first portion of radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer each having a length longer than the first length, the second feed spoke channels having second feed riser ports fluidly connected to a second central plenum of the second radially symmetric gas distribution feature in the fractal layer immediately downstream of the feed layer each having a second length, and The second feed spoke channels having second feed riser ports fluidly connected to a second central plenum of the second portion of radially symmetric gas distribution characteristics in the fractal layer immediately downstream of the feed layer each have a length longer than the second length.

6. The semiconductor processing apparatus of claim 1, wherein the first radially symmetric gas distribution features of the fractal layer each include four first spoke channels, and the second radially symmetric gas distribution features of the fractal layer each include four second spoke channels.

7. The semiconductor processing equipment of claim 6, wherein the first spoke channel and the second spoke channel of the first radially symmetric gas distribution feature and the second radially symmetric gas distribution feature of at least one fractal layer of the fractal layer are respectively at the same height.

8. The semiconductor processing equipment according to claim 6, wherein: For each of the fractal layers: The first spoke channels are each aligned with one of two orthogonal first channel axes, The second spoke channels are each aligned with one of two orthogonal second channel axes, and the first channel axis is 45° out of phase with the second channel axis.

9. The semiconductor processing equipment according to claim 6, wherein: For each of the fractal layers having an immediately adjacent upstream fractal layer, the first radially symmetric gas distribution features of the fractal layer each have a center-to-center spacing between their corresponding first riser ports that is approximately 50% of the corresponding center-to-center spacing between the first riser ports in the first radially symmetric gas distribution features of the immediately adjacent upstream fractal layer.

10. The semiconductor processing equipment according to claim 6, wherein: For each of the fractal layers having an immediately adjacent upstream fractal layer, the second radially symmetric gas distribution features of the fractal layer each have a center-to-center spacing between their corresponding second riser ports that is approximately 50% of the corresponding center-to-center spacing between the second riser ports in the second radially symmetric gas distribution features of the immediately adjacent upstream fractal layer.

11. The semiconductor processing apparatus of claim 6, wherein there are at least three fractal layers.

12. The semiconductor processing equipment according to claim 1, wherein the body is made of a ceramic material.

13. The semiconductor processing apparatus of claim 12, wherein the body is made of a plurality of discrete layers of ceramic material fused together.

14. The semiconductor processing equipment of claim 12, wherein the body is a 3D printed structure.

15. The semiconductor processing equipment according to any one of claims 1 to 14, further comprising: Processing room; as well as A base, wherein: The susceptor is positioned within the processing chamber, and The showerhead is positioned above the susceptor within the processing chamber.

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