Patent Publication Number: US-11049698-B2

Title: Dual-channel showerhead with improved profile

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/285,331 filed Oct. 4, 2016, and titled “DUAL-CHANNEL SHOWERHEAD WITH IMPROVED PROFILE” which is hereby incorporated herein in its entirety by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The present technology relates to semiconductor systems, processes, and equipment. More specifically, the present technology relates to processing chambers that may include showerheads that may be used as a plasma electrode. 
     BACKGROUND 
     Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials. 
     Etch processes, deposition processes, and cleaning processes may be performed in a variety of chambers. These chambers may include components that may be used to form a capacitively-coupled plasma, or may be proximate internal chamber regions where other forms of plasma are produced, such as inductively-coupled plasma, for example. The chamber components may be configured in certain ways to reduce effects of plasma generation or precursor distribution through the chamber, but this may be at the cost of additional functionality. 
     Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology. 
     SUMMARY 
     Semiconductor processing systems and methods of the present technology may include semiconductor processing chambers including a chamber housing at least partially defining an interior region of the semiconductor processing chamber, and the chamber housing may include a lid. The cambers may include a pedestal configured to support a substrate within a processing region of the semiconductor processing chamber. The chambers may include a first showerhead positioned between the lid and the processing region, and may include a faceplate positioned between the first showerhead and the processing region of the semiconductor processing chamber. The chambers may also include a second showerhead positioned within the chamber between the faceplate and the processing region of the semiconductor processing chamber. The second showerhead may include at least two plates coupled together to define a volume between the at least two plates. The at least two plates may at least partially define channels through the second showerhead, and each channel may be characterized by a first diameter at a first end of the channel and may be characterized by a plurality of ports at a second end of the channel. 
     In embodiments each port may be characterized by a diameter less than the first diameter. Additionally, the first showerhead may be coupled with an electrical source, and the faceplate may be coupled with electrical ground. Exemplary semiconductor processing chambers may also include a spacer between the first showerhead and the faceplate. The first showerhead, the faceplate, and the spacer may be configured to at least partially define a plasma processing region within the semiconductor processing chamber. In some embodiments the pedestal may be coupled with an electrical source, and the second showerhead may be coupled with electrical ground. The pedestal and the second showerhead may be configured to at least partially define a plasma processing region within the processing region of the semiconductor processing chamber. In embodiments the faceplate and the second showerhead may be in direct contact, and the faceplate and the second showerhead may both be coupled with electrical ground. 
     The second showerhead may be positioned within the chamber having the first end of each channel facing the faceplate, and having the second end of each channel proximate the processing region of the semiconductor processing chamber. Additionally, the second showerhead may be positioned within the chamber having the first end of each channel proximate the processing region of the semiconductor processing chamber, and having the second end of each channel facing the faceplate. A surface of the second showerhead may be adjacent the processing region of the semiconductor processing chamber, and the surface may be coated or treated. In some embodiments, the first diameter may be at least about 2.5 mm, and a diameter of each port may be less than or about 1.2 mm. 
     The present technology also encompasses showerheads. The showerheads may include a first plate defining a plurality of through-holes. The showerhead may also include a second plate coupled with the first plate. The second plate may define a first plurality of apertures and a second plurality of apertures, and the second plurality of apertures may be defined in the second plate in a plurality of groups of apertures including at least two apertures of the second plurality of apertures. In some embodiments, each through-hole of the first plate may be aligned with at least one group of apertures to produce a channel. 
     In embodiments the first plate and the second plate may be coupled with one another to define a volume between the first plate and the second plate. The volume may be fluidly accessible from the first plurality of apertures of the second plate, and the channels may be fluidly isolated from the volume defined between the first plate and the second plate. The first plurality of apertures may be defined in the second plate in a plurality of first groups of apertures including at least two apertures of the first plurality of apertures, and each first group of apertures may surround a group of apertures of the second plurality of apertures. In some embodiments each first group of apertures may include at least 4 apertures. In some embodiments each through-hole may be characterized by a diameter of at least about 5 mm. Each aperture of the second plurality of apertures may be characterized by a diameter of less than or about 1 mm. Each group of apertures of the second plurality of apertures may include at least about 6 apertures. In some embodiments the second plate may include a material resistant to plasma degradation. 
     The present technology may also encompass showerheads, which may include a first plate defining a first plurality of apertures. The first plurality of apertures may be defined in the first plate in a plurality of groups of apertures including at least two apertures of the first plurality of apertures. The showerheads may also include a second plate coupled with the first plate. The second plate may define a second plurality of apertures and a plurality of through-holes, and each through-hole of the second plate may be aligned with at least one group of apertures of the first plurality of apertures to produce a channel. 
     Such technology may provide numerous benefits over conventional systems and techniques. For example, showerheads of the present technology may provide an improved ground path that may limit plasma leakage. Additionally, the showerheads may limit reaction byproducts from back streaming and contacting other chamber components. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings. 
         FIG. 1  shows a top plan view of an exemplary processing system according to embodiments of the present technology. 
         FIG. 2  shows a schematic cross-sectional view of an exemplary processing chamber according to embodiments of the present technology. 
         FIG. 3  shows a bottom plan view of an exemplary showerhead according to embodiments of the disclosed technology. 
         FIG. 4  shows a plan view of an exemplary faceplate according to embodiments of the disclosed technology. 
         FIG. 5  shows a cross-sectional view of a processing chamber according to embodiments of the present technology. 
         FIG. 6A  shows a top plan view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 6B  shows a bottom plan view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 7A  shows a cross-sectional view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 7B  shows a cross-sectional view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 8A  shows a top plan view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 8B  shows a bottom plan view of an exemplary showerhead according to embodiments of the present technology. 
         FIG. 9  shows operations of an exemplary method according to embodiments of the present technology. 
     
    
    
     Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include additional or exaggerated material for illustrative purposes. 
     In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter. 
     DETAILED DESCRIPTION 
     The present technology includes systems and components for semiconductor processing including tuned etch processes. Certain processing chambers available may include multiple plasma mechanisms, such as one at the wafer level as well as a remote plasma source. Plasma at the wafer level may often be formed via a capacitively-coupled plasma formed between two electrodes. One or both of these electrodes may be or include additional chamber components, such as showerheads, pedestals, or chamber walls. Showerheads may be configured in any number of ways to affect precursor distribution, and may also be used as an electrode in plasma generation. However, showerhead configurations to improve flow profiles in a processing chamber may impact the showerhead performance as an electrode. 
     For example, increased aperture diameter through the showerhead may allow improvements in radical recombination as well as flow uniformity through the showerhead. On the other hand, if the showerhead is also operating as an electrode, increased aperture diameter may allow plasma leakage through the showerhead, which may then interact with other components. For wafer level plasma, larger aperture diameters may also allow reaction byproducts from etching or deposition reactions to backflow through the apertures and contact, deposit, or react with other chamber components. 
     Conventional technologies may have dealt with these phenomena in a number of ways. In one example, an additional plate or showerhead was included in the processing region to prevent or reduce any backflow of materials through the showerhead. However, such a component may increase chamber flow paths for precursors. For radical precursors travelling through the chamber, this may allow recombination or loss of energy to occur, which may reduce the effectiveness of the precursor or plasma effluents. The present technology may overcome these deficiencies by providing improved showerheads that may be utilized in semiconductor processing chambers, including for use with wafer-level plasma generation. The showerheads may include channels having increased diameter on one end to allow adequate precursor flow, and may include ports at an opposite end to prevent plasma and reaction byproducts from flowing back through the showerhead. These designs may protect other chamber components, while also limiting the effect on radical recombination rates. 
     Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers. Accordingly, the technology should not be considered to be so limited as for use with etching processes alone. 
       FIG. 1  shows a top plan view of one embodiment of a processing system  100  of deposition, etching, baking, and curing chambers according to embodiments. The processing tool  100  depicted in  FIG. 1  may contain a plurality of process chambers,  114 A-D, a transfer chamber  110 , a service chamber  116 , an integrated metrology chamber  117 , and a pair of load lock chambers  106 A-B. The process chambers may include structures or components similar to those described in relation to  FIG. 2 , as well as additional processing chambers. 
     To transport substrates among the chambers, the transfer chamber  110  may contain a robotic transport mechanism  113 . The transport mechanism  113  may have a pair of substrate transport blades  113 A attached to the distal ends of extendible arms  113 B, respectively. The blades  113 A may be used for carrying individual substrates to and from the process chambers. In operation, one of the substrate transport blades such as blade  113 A of the transport mechanism  113  may retrieve a substrate W from one of the load lock chambers such as chambers  106 A-B and carry substrate W to a first stage of processing, for example, an etching process as described below in chambers  114 A-D. If the chamber is occupied, the robot may wait until the processing is complete and then remove the processed substrate from the chamber with one blade  113 A and may insert a new substrate with a second blade (not shown). Once the substrate is processed, it may then be moved to a second stage of processing. For each move, the transport mechanism  113  generally may have one blade carrying a substrate and one blade empty to execute a substrate exchange. The transport mechanism  113  may wait at each chamber until an exchange can be accomplished. 
     Once processing is complete within the process chambers, the transport mechanism  113  may move the substrate W from the last process chamber and transport the substrate W to a cassette within the load lock chambers  106 A-B. From the load lock chambers  106 A-B, the substrate may move into a factory interface  104 . The factory interface  104  generally may operate to transfer substrates between pod loaders  105 A-D in an atmospheric pressure clean environment and the load lock chambers  106 A-B. The clean environment in factory interface  104  may be generally provided through air filtration processes, such as HEPA filtration, for example. Factory interface  104  may also include a substrate orienter/aligner (not shown) that may be used to properly align the substrates prior to processing. At least one substrate robot, such as robots  108 A-B, may be positioned in factory interface  104  to transport substrates between various positions/locations within factory interface  104  and to other locations in communication therewith. Robots  108 A-B may be configured to travel along a track system within enclosure  104  from a first end to a second end of the factory interface  104 . 
     The processing system  100  may further include an integrated metrology chamber  117  to provide control signals, which may provide adaptive control over any of the processes being performed in the processing chambers. The integrated metrology chamber  117  may include any of a variety of metrological devices to measure various film properties, such as thickness, roughness, composition, and the metrology devices may further be capable of characterizing grating parameters such as critical dimensions, sidewall angle, and feature height under vacuum in an automated manner. 
     Turning now to  FIG. 2  is shown a cross-sectional view of an exemplary process chamber system  200  according to the present technology. Chamber  200  may be used, for example, in one or more of the processing chamber sections  114  of the system  100  previously discussed. Generally, the etch chamber  200  may include a first capacitively-coupled plasma source to implement an ion milling operation and a second capacitively-coupled plasma source to implement an etching operation and to implement an optional deposition operation. The chamber  200  may include grounded chamber walls  240  surrounding a chuck  250 . In embodiments, the chuck  250  may be an electrostatic chuck that clamps the substrate  202  to a top surface of the chuck  250  during processing, though other clamping mechanisms as would be known may also be utilized. The chuck  250  may include an embedded heat exchanger coil  217 . In the exemplary embodiment, the heat exchanger coil  217  includes one or more heat transfer fluid channels through which heat transfer fluid, such as an ethylene glycol/water mix, may be passed to control the temperature of the chuck  250  and ultimately the temperature of the substrate  202 . 
     The chuck  250  may include a mesh  249  coupled to a high voltage DC supply  248  so that the mesh  249  may carry a DC bias potential to implement the electrostatic clamping of the substrate  202 . The chuck  250  may be coupled with a first RF power source and in one such embodiment, the mesh  249  may be coupled with the first RF power source so that both the DC voltage offset and the RF voltage potentials are coupled across a thin dielectric layer on the top surface of the chuck  250 . In the illustrative embodiment, the first RF power source may include a first and second RF generator  252 ,  253 . The RF generators  252 ,  253  may operate at any industrially utilized frequency, however in the exemplary embodiment the RF generator  252  may operate at 60 MHz to provide advantageous directionality. Where a second RF generator  253  is also provided, the exemplary frequency may be 2 MHz. 
     With the chuck  250  to be RF powered, an RF return path may be provided by a first showerhead  225 , which may include a dual channel showerhead. The first showerhead  225  may be disposed above the chuck to distribute a first feed gas into a first chamber region  284  defined by the first showerhead  225  and the chamber wall  240 . As such, the chuck  250  and the first showerhead  225  form a first RF coupled electrode pair to capacitively energize a first plasma  270  of a first feed gas within a first chamber region  284 . A DC plasma bias, or RF bias, resulting from capacitive coupling of the RF powered chuck may generate an ion flux from the first plasma  270  to the substrate  202 , e.g., Ar ions where the first feed gas is Ar, to provide an ion milling plasma. The first showerhead  225  may be grounded or alternately coupled with an RF source  228  having one or more generators operable at a frequency other than that of the chuck  250 , e.g., 13.56 MHz or 60 MHz. In the illustrated embodiment the first showerhead  225  may be selectably coupled to ground or the RF source  228  through the relay  227  which may be automatically controlled during the etch process, for example by a controller (not shown). In disclosed embodiments, chamber  200  may not include showerhead  225  or dielectric spacer  220 , and may instead include only baffle  215  and showerhead  210  described further below. 
     As further illustrated in the figure, the etch chamber  200  may include a pump stack capable of high throughput at low process pressures. In embodiments, at least one turbo molecular pump  265 ,  266  may be coupled with the first chamber region  284  through one or more gate valves  260  and disposed below the chuck  250 , opposite the first showerhead  225 . The turbo molecular pumps  265 ,  266  may be any commercially available pumps having suitable throughput and more particularly may be sized appropriately to maintain process pressures below or about 10 mTorr or below or about 5 mTorr at the desired flow rate of the first feed gas, e.g., 50 to 500 sccm of Ar where argon is the first feedgas. In the embodiment illustrated, the chuck  250  may form part of a pedestal which is centered between the two turbo pumps  265  and  266 , however in alternate configurations chuck  250  may be on a pedestal cantilevered from the chamber wall  240  with a single turbo molecular pump having a center aligned with a center of the chuck  250 . 
     Disposed above the first showerhead  225  may be a second showerhead  210 . In one embodiment, during processing, the first feed gas source, for example, Argon delivered from gas distribution system  290  may be coupled with a gas inlet  276 , and the first feed gas flowed through a plurality of apertures  280  extending through second showerhead  210 , into the second chamber region  281 , and through a plurality of apertures  282  extending through the first showerhead  225  into the first chamber region  284 . An additional flow distributor or baffle  215  having apertures  278  may further distribute a first feed gas flow  216  across the diameter of the etch chamber  200  through a distribution region  218 . In an alternate embodiment, the first feed gas may be flowed directly into the first chamber region  284  via apertures  283  which are isolated from the second chamber region  281  as denoted by dashed line  223 . 
     Chamber  200  may additionally be reconfigured from the state illustrated to perform an etching operation. A secondary electrode  205  may be disposed above the first showerhead  225  with a second chamber region  281  there between. The secondary electrode  205  may further form a lid or top plate of the etch chamber  200 . The secondary electrode  205  and the first showerhead  225  may be electrically isolated by a dielectric ring  220  and form a second RF coupled electrode pair to capacitively discharge a second plasma  292  of a second feed gas within the second chamber region  281 . Advantageously, the second plasma  292  may not provide a significant RF bias potential on the chuck  250 . At least one electrode of the second RF coupled electrode pair may be coupled with an RF source for energizing an etching plasma. The secondary electrode  205  may be electrically coupled with the second showerhead  210 . In an exemplary embodiment, the first showerhead  225  may be coupled with a ground plane or floating and may be coupled to ground through a relay  227  allowing the first showerhead  225  to also be powered by the RF power source  228  during the ion milling mode of operation. Where the first showerhead  225  is grounded, an RF power source  208 , having one or more RF generators operating at 13.56 MHz or 60 MHz, for example, may be coupled with the secondary electrode  205  through a relay  207  which may allow the secondary electrode  205  to also be grounded during other operational modes, such as during an ion milling operation, although the secondary electrode  205  may also be left floating if the first showerhead  225  is powered. 
     A second feed gas source, such as nitrogen trifluoride, and a hydrogen source, such as ammonia, may be delivered from gas distribution system  290 , and coupled with the gas inlet  276  such as via dashed line  224 . In this mode, the second feed gas may flow through the second showerhead  210  and may be energized in the second chamber region  281 . Reactive species may then pass into the first chamber region  284  to react with the substrate  202 . As further illustrated, for embodiments where the first showerhead  225  is a multi-channel showerhead, one or more feed gases may be provided to react with the reactive species generated by the second plasma  292 . In one such embodiment, a water source may be coupled with the plurality of apertures  283 . Additional configurations may also be based on the general illustration provided, but with various components reconfigured. For example, flow distributor or baffle  215  may be a plate similar to the second showerhead  210 , and may be positioned between the secondary electrode  205  and the second showerhead  210 . 
     As any of these plates may operate as an electrode in various configurations for producing plasma, one or more annular or other shaped spacer may be positioned between one or more of these components, similar to dielectric ring  220 . Second showerhead  210  may also operate as an ion suppression plate in embodiments, and may be configured to reduce, limit, or suppress the flow of ionic species through the second showerhead  210 , while still allowing the flow of neutral and radical species. One or more additional showerheads or distributors may be included in the chamber between first showerhead  225  and chuck  250 . Such a showerhead may take the shape or structure of any of the distribution plates or structures previously described. Also, in embodiments a remote plasma unit (not shown) may be coupled with the gas inlet to provide plasma effluents to the chamber for use in various processes. 
     In an embodiment, the chuck  250  may be movable along the distance H 2  in a direction normal to the first showerhead  225 . The chuck  250  may be on an actuated mechanism surrounded by a bellows  255 , or the like, to allow the chuck  250  to move closer to or farther from the first showerhead  225  as a means of controlling heat transfer between the chuck  250  and the first showerhead  225 , which may be at an elevated temperature of 80° C.-150° C., or more. As such, an etch process may be implemented by moving the chuck  250  between first and second predetermined positions relative to the first showerhead  225 . Alternatively, the chuck  250  may include a lifter  251  to elevate the substrate  202  off a top surface of the chuck  250  by distance H 1  to control heating by the first showerhead  225  during the etch process. In other embodiments, where the etch process is performed at a fixed temperature such as about 90-110° C. for example, chuck displacement mechanisms may be avoided. A system controller (not shown) may alternately energize the first and second plasmas  270  and  292  during the etching process by alternately powering the first and second RF coupled electrode pairs automatically. 
     The chamber  200  may also be reconfigured to perform a deposition operation. A plasma  292  may be generated in the second chamber region  281  by an RF discharge which may be implemented in any of the manners described for the second plasma  292 . Where the first showerhead  225  is powered to generate the plasma  292  during a deposition, the first showerhead  225  may be isolated from a grounded chamber wall  240  by a dielectric spacer  230  so as to be electrically floating relative to the chamber wall. In the exemplary embodiment, an oxidizer feed gas source, such as molecular oxygen, may be delivered from gas distribution system  290 , and coupled with the gas inlet  276 . In embodiments where the first showerhead  225  is a multi-channel showerhead, any silicon-containing precursor, such as OMCTS for example, may be delivered from gas distribution system  290 , and directed into the first chamber region  284  to react with reactive species passing through the first showerhead  225  from the plasma  292 . Alternatively the silicon-containing precursor may also be flowed through the gas inlet  276  along with the oxidizer. Chamber  200  is included as a general chamber configuration that may be utilized for various operations discussed in reference to the present technology. 
       FIG. 3  is a bottom view of a showerhead  325  for use with a processing chamber according to embodiments. Showerhead  325  may correspond with showerhead  225  shown in  FIG. 2 . Through-holes  365 , which may be a view of first fluid channels or apertures  282 , may have a plurality of shapes and configurations in order to control and affect the flow of precursors through the showerhead  225 . Small holes  375 , which may be a view of second fluid channels or apertures  283 , may be distributed substantially evenly over the surface of the showerhead, even amongst the through-holes  365 , and may provide more even mixing of the precursors as they exit the showerhead than other configurations. 
     An arrangement for a faceplate according to embodiments is shown in  FIG. 4 . As shown, the faceplate  400  may include a perforated plate or manifold. The assembly of the faceplate may be similar to the showerhead as shown in  FIG. 3 , or may include a design configured specifically for distribution patterns of precursor gases. Faceplate  400  may include an annular frame  410  positioned in various arrangements within an exemplary processing chamber, such as the chamber as shown in  FIG. 2 . On or within the frame may be coupled a plate  420 , which may be similar in embodiments to ion suppressor plate  523  as described below. In embodiments faceplate  400  may be a single-piece design where the frame  410  and plate  420  are a single piece of material. 
     The plate may have a disc shape and be seated on or within the frame  410 . The plate may be a conductive material such as a metal including aluminum, as well as other conductive materials that allow the plate to serve as an electrode for use in a plasma arrangement as previously described. The plate may be of a variety of thicknesses, and may include a plurality of apertures  465  defined within the plate. An exemplary arrangement as shown in  FIG. 4  may include a pattern as previously described with reference to the arrangement in  FIG. 3 , and may include a series of rings of apertures in a geometric pattern, such as a hexagon as shown. As would be understood, the pattern illustrated is exemplary and it is to be understood that a variety of patterns, hole arrangements, and hole spacing are encompassed in the design. 
     The apertures  465  may be sized or otherwise configured to allow fluids to be flowed through the apertures during operation. The apertures may be sized less than about 2 inches in various embodiments, and may be less than or about 1.5 inches, about 1 inch, about 0.9 inches, about 0.8 inches, about 0.75 inches, about 0.7 inches, about 0.65 inches, about 0.6 inches, about 0.55 inches, about 0.5 inches, about 0.45 inches, about 0.4 inches, about 0.35 inches, about 0.3 inches, about 0.25 inches, about 0.2 inches, about 0.15 inches, about 0.1 inches, about 0.05 inches, about 0.04 inches, about 0.035 inches, about 0.03 inches, about 0.025 inches, about 0.02 inches, about 0.015 inches, about 0.01 inches, etc. or less. 
     In some embodiments faceplate  400  may operate as an ion suppressor that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of a chamber plasma region while allowing uncharged neutral or radical species to pass through the ion suppressor into an activated gas delivery region downstream of the ion suppressor. In embodiments, the ion suppressor may be a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor is reduced. 
     Turning to  FIG. 5  is shown a simplified schematic of processing system  500  according to the present technology. The chamber of system  500  may include any of the components as previously discussed with relation to  FIGS. 2-4 , and may be configured to house a semiconductor substrate  555  in a processing region  560  of the chamber. The chamber housing  503  may at least partially define an interior region of the chamber. For example, the chamber housing  503  may include lid  502 , and may at least partially include any of the other plates or components illustrated in the figure. For example, the chamber components may be included as a series of stacked components with each component at least partially defining a portion of chamber housing  503 . The substrate  555  may be located on a pedestal  565  as shown. Processing chamber  500  may include a remote plasma unit (not shown) coupled with inlet  501 . In other embodiments, the system may not include a remote plasma unit. 
     With or without a remote plasma unit, the system may be configured to receive precursors or other fluids through inlet  501 , which may provide access to a mixing region  511  of the processing chamber. The mixing region  511  may be separate from and fluidly coupled with the processing region  560  of the chamber. The mixing region  511  may be at least partially defined by a top of the chamber of system  500 , such as chamber lid  502  or lid assembly, which may include an inlet assembly for one or more precursors, and a distribution device, such as faceplate  509  below. Faceplate  509  may be similar to the showerhead or faceplate illustrated in  FIGS. 3-4  in disclosed embodiments. Faceplate  509  may include a plurality of channels or apertures  507  that may be positioned and/or shaped to affect the distribution and/or residence time of the precursors in the mixing region  511  before proceeding through the chamber. 
     For example, recombination may be affected or controlled by adjusting the number of apertures, size of the apertures, or configuration of apertures across the faceplate  509 . As illustrated, faceplate  509  may be positioned between the mixing region  511  and the processing region  560  of the chamber, and the faceplate  509  may be configured to distribute one or more precursors through the chamber  500 . The chamber  500  may include one or more of a series of components that may optionally be included in disclosed embodiments. For example, although faceplate  509  is described, in some embodiments the chamber may not include such a faceplate. In disclosed embodiments, the precursors that are at least partially mixed in mixing region  511  may be directed through the chamber via one or more of the operating pressure of the system, the arrangement of the chamber components, or the flow profile of the precursors. 
     Chamber  500  may additionally include a first showerhead  515 . Showerhead  515  may have any of the features or characteristics of the plates discussed with respect to  FIGS. 3-4 . Showerhead  515  may be positioned within the semiconductor processing chamber as illustrated, and may be included or positioned between the lid  502  and the processing region  560 . In embodiments, showerhead  515  may be or include a metallic or conductive component that may be a coated, seasoned, or otherwise treated material. Exemplary materials may include metals, including aluminum, as well as metal oxides, including aluminum oxide. Depending on the precursors being utilized, or the process being performed within the chamber, the showerhead may be any other metal or material that may provide structural stability as well as conductivity as may be utilized. 
     Showerhead  515  may define one or more apertures  517  to facilitate uniform distribution of precursors through the showerhead. The apertures  517  may be included in a variety of configurations or patterns, and may be characterized by any number of geometries that may provide precursor distribution as may be desired. Showerhead  515 , may be electrically coupled with a power source in embodiments. For example, showerhead  515  may be coupled with an RF source  519  as illustrated. When operated, RF source  519  may provide a current to showerhead  515  allowing a capacitively-coupled plasma (“CCP”) to be formed between the showerhead  515  and another component. 
     An additional faceplate or device  523  may be disposed below the showerhead  515 . Faceplate  523  may include a similar design as faceplate  509 , and may have a similar arrangement as is illustrated at  FIG. 3 or 4 , for example. In embodiments, faceplate  523  may be positioned within the semiconductor processing chamber between the showerhead  515  and the processing region  560 . Spacer  510  may be positioned between the showerhead  515  and plate  523 , and may include a dielectric material. Apertures  524  may be defined in plate  523 , and may be distributed and configured to affect the flow of ionic species through the plate  523 . For example, the apertures  524  may be configured to at least partially suppress the flow of ionic species directed toward the processing region  560 , and may allow plate  523  to operate as an ion suppressor as previously described. The apertures  524  may have a variety of shapes including channels as previously discussed, and may include a tapered portion extending outward away from the processing region  560  in disclosed embodiments. 
     Faceplate  523  may be coupled with an electrical ground  534 , which may allow a plasma to be generated in embodiments. For example, showerhead  515 , faceplate  523 , and spacer  510  may at least partially define a plasma processing region  533  within the semiconductor processing chamber. Precursors may be provided through the inlet  501  and distributed through faceplate  509  and showerhead  515  to plasma processing region  533 . Showerhead  515  may be charged relative to ground at faceplate  523 , and the precursors may be energized to produce a plasma within the plasma processing region  533 . The plasma effluents may then be flowed through faceplate  523  towards processing region  560  to interact with substrate or wafer  555 , or materials on the substrate. 
     The chamber  500  may further include a gas distribution assembly  535 , which may also be a second showerhead, within the chamber. For example, gas distribution assembly  535  may at least partially define processing region  560 , and may distribute precursors to that region. In order to provide uniform processing on substrate  555 , gas distribution assembly  535  may be configured to provide a more uniform flow of precursors into processing region  560 . The gas distribution assembly  535 , which may be similar in aspects to the dual-channel showerheads as previously described, may be located within the chamber above the processing region  560 , such as between the processing region  560  and the lid  502 , and may be positioned between the processing region  560  and the faceplate  523 . The gas distribution assembly  535  may be configured to deliver both a first and a second precursor into the processing region  560  of the chamber. In embodiments, the gas distribution assembly  535  may at least partially divide the interior region of the chamber into a remote region and a processing region in which substrate  555  is positioned. 
     Although the exemplary system of  FIG. 5  includes a dual-channel showerhead, it is understood that alternative distribution assemblies may be utilized that maintain a precursor fluidly isolated from species introduced through inlet  501 . For example, a perforated plate and tubes underneath the plate may be utilized, although other configurations may operate with reduced efficiency or may not provide as uniform processing as the dual-channel showerhead as described. By utilizing one of the disclosed designs, a precursor may be introduced into the processing region  560  that is not previously excited by a plasma prior to entering the processing region  560 , or may be introduced to avoid contacting an additional precursor with which it may react. Although not shown, an additional spacer may be positioned between the faceplate  523  and the showerhead  535 , such as an annular spacer, to isolate the plates from one another. In embodiments in which an additional precursor may not be included, the gas distribution assembly  535  may have a design similar to any of the previously described components, and may include characteristics similar to the faceplate illustrated in  FIG. 4 . 
     In embodiments, gas distribution assembly  535  may include an embedded heater  539 , which may include a resistive heater or a channel for a temperature controlled fluid, for example. The gas distribution assembly  535  may include an upper plate and a lower plate in embodiments, and may include a plurality of plates coupled with one another, which may include more than or about 2 plates, more than or about 3 plates, more than or about 4 plates, more than or about 5 plates, or more depending on the configuration or spacing within the gas distribution assembly  535 . The plates may be coupled with one another to define a volume  537  between the plates. The coupling of the plates may be such as to provide first fluid channels  540  through the upper and lower plates, and second fluid channels  545  through the lower plate. The second formed channels may be configured to provide fluid access from the volume  537  through the lower plate, and the first fluid channels  540  may be fluidly isolated from the volume  537  between the plates and the second fluid channels  545 . The volume  537  may be fluidly accessible through a side of the gas distribution assembly  535 , such as channel  223  as previously discussed. The channel may be coupled with an access in the chamber separate from the inlet  501  of the chamber  500 . 
     Gas distribution assembly  535  may be utilized in a plasma processing operation as well, and in examples may be electrically coupled with a source or electrical ground, such as electrical ground  544 , for example. By coupling gas distribution assembly  535  with electrical ground, the gas distribution assembly  535  may be of a similar potential as faceplate  523 , and thus may prevent plasma from being formed between the two components. In some embodiments, faceplate  523  and gas distribution assembly  535  may be in direct contact as illustrated, and may be both coupled with electrical ground. Pedestal  565  may be coupled with an electrical source  554 , which in combination with a grounded gas distribution assembly  535  may at least partially define an additional plasma processing region within processing region  560  of the semiconductor processing chamber. By providing plasma processing capabilities at the wafer level, additional operations may be performed, such as material modification as discussed previously, as well as etching and deposition operations that may benefit from plasma processing. 
     In some embodiments, a plasma as described above may be formed in a region of the chamber remote from the processing region, such as in plasma processing region  533 , as well as within a plasma processing region within the processing region  560 . Each of these plasma regions may be capacitively-coupled plasma configurations in embodiments, although other plasma generation components may be included, such as coils to provide an inductively-coupled plasma region. The faceplates, showerheads, chamber walls, spacers, and pedestal, which may each be contacted by plasma may additionally be coated or seasoned in order to minimize the degradation of the components between which the plasma may be formed. The plates may additionally include compositions that may be less likely to degrade or be affected including ceramics, metal oxides, or other conductive materials. 
     Operating a conventional capacitively-coupled plasma (“CCP”) may degrade the chamber components, which may remove particles that may be inadvertently distributed on a substrate. Such particles may affect performance of devices formed from these substrates due to the metal particles that may provide short-circuiting across semiconductor substrates. However, the CCP of the disclosed technology may be operated at reduced or substantially reduced power in embodiments, and may be utilized to maintain the plasma as may be produced by a remote plasma unit, instead of ionizing species within the plasma region. In other embodiments the CCP may be operated to ionize precursors delivered into the region. For example, the CCP may be operated at a power level below or about 1 kW, 500 W, 250 W, 100 W, 50 W, 20 W, etc. or less. Moreover, the CCP may produce a flat plasma profile which may provide a uniform plasma distribution within the space. As such, a more uniform flow of plasma effluents may be delivered downstream to the processing region of the chamber. 
     Forming plasma at the wafer level may be beneficial for processing operations as discussed previously. However, when a component such as gas distribution assembly  535  is incorporated as part of the plasma processing equipment, additional considerations for plasma formation may be involved. First fluid channels  540  may be included to allow plasma effluents to be provided to the chamber region. In order to provide adequate flow, and to reduce interaction with plasma effluents, the channels may be characterized by an increased diameter, such as greater than or about 2.5 mm, for example. However, when gas distribution assembly  535  is involved in a capacitively-coupled plasma operation, these aperture sizes may pose issues. 
     For example, plasma may generally be formed in regions having a length greater than a Debye length. When the first fluid channels  540  are characterized by increased diameter, then the surface of the assembly facing the plasma processing region may not provide RF continuity across the surface. Consequently, plasma may be generated within first fluid channels  540 , and may also leak back through these channels toward the faceplate  523 . One or more of the surfaces of gas distribution assembly  535  may be coated or treated to reduce degradation from plasma. Similarly, one or more surfaces of faceplate  523  may be coated or treated to reduce degradation from plasma. However, the surfaces coated or treated on each component may not be facing one another. 
     For example, as illustrated in  FIG. 5 , the surfaces of gas distribution assembly  535  that are facing, proximate, or adjacent processing region  560  may be treated, but the surfaces facing faceplate  523  may not be coated or treated. Similarly, the surfaces of faceplate  523  that are facing, proximate, or adjacent plasma processing region  533  may be coated or treated, but the surfaces facing gas distribution assembly  535  may not be coated or treated. Accordingly, plasma leaking into the region between faceplate  523  and gas distribution assembly  535  may be able to degrade untreated portions of the components. Although first fluid channels  540  may be reduced in diameter to prevent this interaction, such a reduction may increase recombination and interaction with plasma effluents produced in plasma processing region  533 . Another solution may include incorporating an additional showerhead having smaller apertures between the gas distribution assembly  535  and the pedestal  565  to reduce backflow of plasma. However, this solution may be unacceptable in certain situations due to the increased travel length for precursors, and because the additional showerhead may produce the same recombination being avoided with the gas distribution assembly. For example, in certain deposition operations residence time of certain precursors, such as trisilylamine or NH radicals or ions, may be controlled to provide acceptable deposition, and the flow path may be relatively unimpeded to prevent deposition on components. By incorporating an additional showerhead, both the flow path length may be increased, and the flow path may be impeded. 
     Accordingly, the present technology may improve on these situations by adjusting the first fluid channels  540  themselves. For example, showerheads or gas distribution assemblies according to the present technology may include fluid channels where each channel may be characterized by a first diameter at a first end of the channel, and may be characterized by a plurality of ports at a second end of the channel. The following figures will discuss exemplary showerheads or gas distribution assemblies that may be used within chambers according to the present technology, such as may be used as gas distribution assembly  535  of chamber  500 , for example. The showerheads may also be used in any other chamber, including other plasma chambers, that may benefit from the improved control discussed throughout the present disclosure. 
       FIG. 6A  shows a top plan view of an exemplary showerhead  600  according to embodiments of the present technology. Showerhead  600  may include any of the components or characteristics of any of the previous showerheads or faceplates discussed throughout the present disclosure. As illustrated, showerhead  600  may include a first plate  610  defining a plurality of through-holes  620  across a surface of the first plate  610 . First plate  610  may be or include a conductive material, which may include aluminum, aluminum oxide, other metals, other metal oxides such as yttrium oxide, for example, or other treated or coated materials. Through-holes  620  may illustrate a first end of first fluid channels  540  as previously described, for example. The through-holes  620  may be characterized by a diameter less than or about 50 mm, for example, and may be characterized by a diameter less than or about 40 mm, less than or about 30 mm, less than or about 20 mm, less than or about 15 mm, less than or about 12 mm, less than or about 10 mm, less than or about 9 mm, less than or about 8 mm, less than or about 7 mm, less than or about 6 mm, less than or about 5 mm, less than or about 4 mm, less than or about 3 mm, less than or about 2 mm, or less in embodiments. 
     Through-holes  620  may be characterized by a diameter greater than or about 4 mm in embodiments, in order to provide adequate flow capabilities for precursors. For example, diameters less than or about 5 mm may impact recombination or other characteristics of precursors flowing through the chamber, including plasma effluents produced in a remote region of the chamber. Accordingly, in some embodiments the diameter of through-holes  620  may be maintained above or about 2.5 mm, greater than or about 3 mm, greater than or about 3.5 mm, greater than or about 4 mm, greater than or about 4.5 mm, greater than or about 5 mm, greater than or about 5.5 mm, greater than or about 6 mm, greater than or about 6.5 mm, greater than or about 7 mm, or greater to prevent a greater impact on precursors or plasma effluents. The diameters may also be a combination of any of the numbers provided or encompassed, and may be ranges included within any of the defined ranges. Depending on the size of showerhead  600  and apertures  620 , first plate  610  may define up to, greater than, or about 500 apertures, and may define up to, greater than, or about 1,000 apertures, about 2,000 apertures, about 3,000 apertures, about 4,000 apertures, about 5,000 apertures, about 6,000 apertures, about 7,000 apertures, about 8,000 apertures, about 9,000 apertures, about 10,000 apertures, or more in embodiments. 
     Through-holes  620  may also provide a view through the formed channel to a second plate  650  that may be coupled with the first plate  610 . In some embodiments, the showerhead  600  may include more than two plates, or only a single plate with defined features. Second plate  650  may include defined ports  660  as viewed through through-holes  620  of first plate  610 . Turning to  FIG. 6B  shows a bottom plan view of exemplary showerhead  600  according to embodiments of the present technology. The figure shows a view of second plate  650  of showerhead  600 . As noted, second plate  650  may include ports  660  defined throughout the second plate  650 , which may be included at a second end of a fluid channel produced through the showerhead  600 . In embodiments, each port  660  may be characterized by a diameter of less than the diameter of through-holes  620 . 
     As explained previously, ports  660  may prevent plasma from leaking through showerhead  600  and may also prevent byproducts of local plasma operations from flowing upstream through showerhead  600 . Accordingly, ports  660  may be characterized by a diameter less than or about 2 mm in embodiments, and may be characterized by a diameter of less than or about 1.5 mm, less than or about 1.2 mm, less than or about 1.0 mm, less than or about 0.9 mm, less than or about 0.8 mm, less than or about 0.7 mm, less than or about 0.6 mm, less than or about 0.5 mm, less than or about 0.4 mm, less than or about 0.3 mm, less than or about 0.2 mm, less than or about 0.1 mm, or less in embodiments. For example, ports  660  may be characterized by a diameter of between about 0.1 mm and about 1.2 mm in embodiments, and may be characterized by a diameter of between about 0.2 mm and about 1 mm in embodiments. The smaller ports  660  may provide improved RF continuity across the showerhead  600 , which may be operating as a ground electrode, for example. The improved RF continuity may allow plasma to be contained below showerhead  600 , or substantially contained below showerhead  600  in embodiments. Additionally, smaller ports  660  may also prevent reaction byproducts from flowing up through through-holes  620  and contacting additional components. 
     As illustrated, ports  660  may be defined in groups of ports across the surface of plate  650 . Each group of ports may include at least or about 2 ports in embodiments, and may include at least or about 3 ports, at least or about 4 ports, at least or about 5 ports, at least or about 6 ports, at least or about 7 ports, at least or about 8 ports, at least or about 9 ports, at least or about 10 ports, at least or about 11 ports, at least or about 12 ports, at least or about 13 ports, at least or about 14 ports, at least or about 15 ports, at least or about 16 ports, at least or about 17 ports, at least or about 18 ports, at least or about 20 ports, at least or about 25 ports, at least or about 30 ports, at least or about 40 ports, at least or about 50 ports, or more ports in embodiments. Ports  660  or groups of ports  660  may be aligned with through-holes  620  in embodiments to provide fluid channels. In embodiments, each group of ports  660  may be axially aligned with a central axis of a through-hole  620 . 
     Second plate  650  may also define additional apertures  670  positioned relative to through-holes  620 , shown hidden as the sidewalls may not be visible through ports  660 . Apertures  670  may be defined about through-holes  620  and ports  660  in embodiments. Apertures  670  may be similar to the second fluid channels  545  previously described, which may provide fluid access from an internal volume showerhead  600 . Accordingly, a precursor flowed through the volume defined between the first plate and the second plate may exit the showerhead  600  through apertures  670 , where the precursor, which may be an excited or unexcited precursor, may then interact with one or more precursors that have been flowed through ports  660 , which may include plasma effluents produced upstream. In embodiments, apertures  670  may be the same size or within the same ranges of sizes as ports  660 , which may also maintain RF continuity across the plate  650 . Accordingly, apertures  670  may be a first plurality of apertures defined in plate  650 , and ports  660  may be a second plurality of apertures defined in plate  650 . As illustrated, apertures  670  may be defined as groups across the showerhead  600  to provide uniformity of flow of a precursor from the volume defined within the showerhead  600 . In embodiments each group of apertures  670  may be formed about groups of ports  660  to provide more uniform contact of precursors flowing from the apertures  670  and ports  660 . In embodiments, each group may include any of the numbers of apertures within the groups as discussed above with respect to ports  660 . 
     Showerhead  600  may be included in a chamber, such as chamber  500 , and may be positioned similar to gas distribution assembly  535  as discussed previously. Accordingly, showerhead  600  may be positioned so that first plate  610  faces towards a lid of the chamber, or towards components such as faceplate  523 . Second plate  650  may face towards a processing region or may be adjacent a processing region, and may at least partially define a plasma processing region within the processing region, such as with a pedestal or other component. Accordingly, second plate  650  may be exposed to plasma, and thus exposed surfaces of second plate  650  may be coated or treated in embodiments to protect the second plate of showerhead  600  from plasma degradation. In other embodiments second plate  650  may be or include a material designed to be resistant to plasma degradation, and may not have an additional coating, which may ease manufacturing depending on the material used. 
       FIG. 7A  shows a cross-sectional view of exemplary showerhead  600  according to embodiments of the present technology. The illustrated showerhead may include any of the features or characteristics previously described. As illustrated, showerhead  600  may include a first plate  610  and a second plate  650 . First plate  610  may define through-holes  620 , which may align with ports  660  defined in second plate  650  to produce fluid channels through showerhead  600 . The ports  660  may be surrounded or have apertures  670  about the ports  660  as previously described. First plate  610  and second plate  650  may be coupled with one another to define a volume  680  between the first plate  610  and the second plate  650 . As illustrated, the volume  680  may be fluidly accessible from the apertures  670 . Additionally, the channels formed by the through-holes  620  and ports  660  may be fluidly isolated from the volume defined between the first plate  610  and the second plate  650 . 
     Showerhead  600  may include channels formed from through-holes  620  and ports  660 , which may include a first end of each channel at the through-holes  620  in first plate  610 , and a second end of each channel at the ports  660  in the second plate  650 . Accordingly, if showerhead  600  may be incorporated within chamber  500 , such as included as a gas distribution assembly like assembly  535 , the first ends of the channels formed may face towards the lid  502  or faceplate  523 . Additionally, the second ends of each channel formed may face towards the pedestal, and may be proximate the processing region  660 , for example. 
     Second plate  650  may define ports  660  through the structure of the second plate  650 , but the thickness of ports  660  may not be equal to the thickness of second plate  650  in embodiments. However, in other embodiments the length of the ports  660  may be equal to the thickness of second plate  650 . In embodiments in which the lengths of the ports  660  are not equal to the thickness of the second plate  650 , a portion of the channel formed may be included in the second plate  650 , and may resemble a counterbore structure in some ways, although multiple ports  660  may be included in the structure. Second plate  650  may be characterized by a thickness  690  through which ports  660  are defined. This thickness may be less than the thickness of second plate  650  to reduce an effect on plasma effluents that may be flowed through the formed channels. 
     For example, if the ports were formed through the entire thickness of the second plate  650 , they may impact precursors or plasma effluents flowing through the formed channels, which may increase recombination, cause deposition to occur prematurely, or other consequences. Accordingly, the thickness  690  of second plate  650  in regions where ports  660  are defined may be less than or about 3 mm in embodiments, and may be less than or about 2.5 mm, less than or about 2 mm, less than or about 1.8 mm, less than or about 1.6 mm, less than or about 1.5 mm, less than or about 1.4 mm, less than or about 1.3 mm, less than or about 1.2 mm, less than or about 1.1 mm, less than or about 1.0 mm, less than or about 0.9 mm, less than or about 0.8 mm, less than or about 0.7 mm, less than or about 0.6 mm, less than or about 0.5 mm, less than or about 0.4 mm, less than or about 0.3 mm, less than or about 0.2 mm, or less in embodiments. Additionally, the thickness of second plate  650  in regions where ports  660  are formed may be between about 0.1 mm and about 2 mm, or may be between about 0.4 mm and about 1.6 mm in embodiments, along with a smaller range within any of the discussed ranges, or some range formed from any of the numbers discussed. In this way, the ports may have a reduced or minimal impact on precursors or plasma effluents flowing through the channels formed through the showerhead  600 . This may provide an additional benefit over including another showerhead as discussed previously, because such a showerhead may not be capable of being machined to such reduced thicknesses, and therefore may provide more of an impact on the precursors or plasma effluents than the ports described throughout the present disclosure. 
     Turning to  FIG. 7B  is shown a cross-sectional view of an exemplary showerhead  700  according to embodiments of the present technology. Showerhead  700  may be similar in some ways to showerhead  600 , and may include any of the features or characteristics discussed for that showerhead or for any of the other showerheads or faceplates discussed. Showerhead  700  may differ from showerhead  600  in that ports  760  may be included on the opposite end of the formed channels through the plates. For example, showerhead  700  may include a first plate  710  and a second plate  750 , which when coupled may define a volume  780  between the first plate  710  and second plate  750 . First plate  710  may define a portion of through-holes  720  and second plate  750  may define a second portion of through-holes  720 . Second plate  750  may also define apertures  770 . Apertures  770  and through-holes  720  may be characterized by any of the dimensions or features previously discussed for various faceplates and showerheads. 
     In some embodiments, showerhead  700  may be characterized by a third plate  755 , which may be coupled with first plate  710  on a surface opposite the surface with which it may be coupled with second plate  750 . In other embodiments, third plate  755  may be a portion of first plate  710 , which may include a counter-bore-like structure similar to that described previously. Third plate  755  may define ports  760 , which may have any of the features or characteristics of previously described ports. Similarly, the thickness  790  of third plate  755 , or the regions of first plate  710  in which ports  760  may be formed, may be similar to the thicknesses described previously to limit interaction with produced plasma effluents or precursors, while providing improved RF continuity across showerhead  700  to reduce or eliminate plasma leakage through the showerhead  700 . In this exemplary showerhead  700 , the assembly may be included in a chamber, such as chamber  500 , similarly to gas distribution assembly  535 . Showerhead  700  may be positioned within the chamber where the first ends of the channels formed through the showerhead may be facing the processing region  560 , while the second ends of the channels may be facing towards lid  502  or faceplate  523 . 
       FIG. 8A  shows a top plan view of exemplary showerhead  700  according to embodiments of the present technology. As illustrated, instead of including the through-holes, third plate  755 , which may be a portion of first plate  710 , may define a plurality of apertures  760  through the plate, which may be ports as previously discussed. The plurality of apertures  760  may be defined in a first plurality of groups of apertures, which may include at least two apertures of the first plurality of apertures. The groups may include any number of apertures as previously described. 
       FIG. 8B  shows a bottom plan view of exemplary showerhead  700  according to embodiments of the present technology. The illustrated view includes second plate  750 , which may be coupled with the first and/or third plate in embodiments. Second plate  750  may define a plurality of through-holes  720 , which may provide access to ports  760  defined in third plate  755  as illustrated. Each through-hole may be aligned with at least one group of apertures from the first plurality of apertures to produce a channel, which may include any of the characteristics previously described. Second plate  750  may also define a plurality of second apertures  770 , which may provide access to an internal volume of the showerhead. The apertures may be defined or arranged in any of the patterns previously discussed. 
     The chambers and plasma sources described above may be used in one or more methods.  FIG. 9  shows operations of an exemplary method  900  according to embodiments of the present technology. Method  900  may include flowing one or more precursors into a chamber at operation  905 . The chamber may be similar to any of the chambers previously described, and may include a showerhead such as any of the showerheads discussed. The precursors may be flowed from an inlet assembly or from an additional access, such as from an access to the volume between plates of a showerhead, for example. The precursors may be flowed into a processing region in which a plasma may be formed at operation  910 . The plasma may be formed as a capacitively-coupled plasma in embodiments, and the electrodes may include the pedestal on which a substrate is positioned as well as a showerhead, such as previously described. The formed plasma may be contained, substantially contained, or essentially contained within the processing region at least partially defined by the showerhead. For example, the showerhead may have features or characteristics such as previously described so that plasma leakage is controlled or eliminated through the showerhead at operation  915 . 
     The chambers and showerheads may also be used in operations in which precursors are provided or plasma effluents are generated remotely, such as either external to the chamber, or within a chamber region upstream of the processing region of the chamber. For example, the plasma effluents may be generated between a showerhead and faceplate as previously described. The plasma effluents may be flowed through a showerhead including channels defined through the showerhead. The channels may be characterized by a first end having a first diameter, and a second end including a number of ports, where each port may be characterized by a diameter less than the first diameter. Either end of the channel may be proximate the processing region in which a substrate may be positioned. The plasma effluents may flow through the channels, which may have a limited impact on recombination at least in part due to the channel dimensions and the port lengths. Additionally, the effluents may perform etching and/or deposition within the processing region, and byproducts may be prevented from flowing upstream through the channels to the faceplate. By including ports within a defined thickness of material at an end of larger channels, showerheads of the present technology may improve on any of these operations compared to conventional showerheads, which may provide plasma and byproduct leakage through the channels of the showerhead. 
     In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details. 
     Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. 
     Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. 
     As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “an apertures” includes a plurality of such apertures, and reference to “the precursor” includes reference to one or more precursors and equivalents thereof known to those skilled in the art, and so forth. 
     Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.