Patent Publication Number: US-10790120-B2

Title: Showerhead having a detachable high resistivity gas distribution plate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 15/909,118, filed Mar. 1, 2018 and U.S. patent application Ser. No. 14/729,736, filed Jun. 3, 2015, which claims benefit of U.S. provisional patent application Ser. No. 62/020,837, filed Jul. 3, 2014. Each of the aforementioned related patent applications is herein incorporated by reference, in its entirety. 
    
    
     FIELD 
     Embodiments of the present disclosure generally relate to semiconductor processing equipment. 
     BACKGROUND 
     Conventional showerheads utilized in semiconductor process chambers (e.g., deposition chambers, etch chambers, or the like) typically include a gas distribution plate permanently bonded to a body. The gas distribution plate is periodically replaced due to degradation caused by exposure to plasma during plasma processes. However, the inventors have observed that since the gas distribution plate is permanently bonded to the body, the entire showerhead assembly is replaced in order to replace the gas distribution plate, thus making the replacement process costly. In addition, arcing has been observed in applications in which a high source power process is performed using gas distribution plates with low electrical resistivity (e.g., 0.005-0.015 ohm-cm). 
     Therefore, the inventors have provided embodiments of an improved showerhead with detachable gas distribution plate. 
     SUMMARY 
     Embodiments of showerheads having a detachable gas distribution plate are provided herein. In some embodiments, a showerhead for use in a semiconductor processing chamber may include a body having a first side and a second side opposing the first side; a gas distribution plate disposed proximate the second side of the body, wherein the gas distribution plate is formed from a material having an electrical resistivity between about 60 ohm-cm to 90 ohm-cm; a clamp disposed about a peripheral edge of the gas distribution plate to removably couple the gas distribution plate to the body; and a thermal gasket disposed in a gap between the body and gas distribution plate. 
     In some embodiments, a process chamber may include a chamber body having a substrate support disposed within an inner volume of the chamber body; and a showerhead disposed within the inner volume of the chamber body opposite the substrate support. The showerhead includes: a body having a first side and a second side opposing the first side, wherein the first side of the body is coupled to a component of the process chamber; a gas distribution plate disposed proximate the second side of the body, wherein the gas distribution plate is formed from a material having an electrical resistivity between about 60 ohm-cm to 90 ohm-cm; a clamp disposed about a peripheral edge of the gas distribution plate to removably couple the gas distribution plate to the body; and a thermal gasket disposed in a gap between the body and gas distribution plate. 
     In some embodiments, a showerhead for use in a semiconductor processing chamber may include a body having a first side and a second side opposing the first side, the second side including an yttrium fluoride coating; a gas distribution plate disposed proximate the second side of the body, wherein the gas distribution plate is formed from a material having an electrical resistivity between about 60 ohm-cm to 90 ohm-cm; an anodized clamp disposed about a peripheral edge of the gas distribution plate to removably couple the gas distribution plate to the body; a plurality of silicone thermal gaskets disposed in a gap between the body and gas distribution plate; and a plurality of pins pressed into the second side of the body and disposed in the gap to maintain a thickness of the gap when the gas distribution plate deflects toward the body. 
     Other and further embodiments of the present disclosure are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. However, the appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  depicts a showerhead with a gas distribution plate in accordance with some embodiments of the present disclosure. 
         FIG. 2  depicts a process chamber suitable for use with a showerhead having a gas distribution plate in accordance with some embodiments of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments of showerheads having a detachable gas distribution plate are provided herein. In at least some embodiments, the inventive showerhead may advantageously allow for the removal and replacement of the gas distribution plate, thus providing a showerhead having a longer useful life and a more cost efficient manner of replacing the gas distribution plate as compared to conventional showerheads having a permanently bonded gas distribution plate. 
       FIG. 1  depicts a showerhead with a gas distribution plate in accordance with some embodiments of the present disclosure. The showerhead  100  generally comprises a body  102 , a gas distribution plate  104  and a clamp  110  configured to removably couple the gas distribution plate to the body  102 . 
     The body  102  comprises a first side  150 , a second side  140  and a plurality of through holes  116  formed in the body  102  extending from the first side  150  to the second side  140 . The plurality of through holes  116  facilitate the passage of process gases through the body  102  to the gas distribution plate  104 . In some embodiments, the through holes  116  may be counter sunk (e.g., countersink  118  shown) to reduce a residual electrical field at the through holes  116  and to facilitate a more uniform gas flow to the gas distribution plate  104 . In some embodiments, a cavity  114  may be formed in first side  150  of the body  102  to facilitate more even distribution of process gases to the plurality of through holes  116 . The body  102  may be fabricated from any suitable process compatible material, for example, such as aluminum. By fabricating the body  102  from a conductive material such as aluminum, the body  102  may function as an electrode to facilitate, for example, the formation of a plasma from process gases provided to the showerhead  100 . In some embodiments the second side  140  of the body  102  may be coated with a material to protect the second side  140  from ions, plasma, or light up. For example, in some embodiments, the coating may be an yttrium fluoride (YF 3 ) coating. The coating may be disposed on the second side  140  of the body  102  using various techniques. Some exemplary non-limiting methods for coating the second side  140  of the body  102  may include deposition or evaporation of the coating onto the body  102  from a target made from or otherwise including the coating material using an electron-beam induced activation of the target material. 
     In some embodiments, one or more channels may be formed in the surfaces of the body  102  to accommodate one or more O-rings and/or radio frequency (RF) gaskets (O-rings  130 ,  132 ,  134  and RF gaskets  108 ,  126  shown). When present, the O-rings  130 ,  132 ,  134  provide a seal between the body  102  and clamp  110  or surfaces of the process chamber (not shown). The O-rings  130 ,  132 ,  134 , may be fabricated from any material suitable to facilitate the aforementioned seal, for example, rubber. The RF gaskets  108 ,  126  facilitate conductivity of RF power from, for example, an RF source to the body  102  and the clamp  110 . For example, RF power may be provided from an RF power supply (such as the RF power supply  286  described below) to a component coupled to the body  102  and in contact with one or more RF gaskets (e.g., RF gasket  126 ). The RF gaskets  108 ,  126  may be fabricated from any suitable conductive material, for example stainless steel. 
     The gas distribution plate  104  facilitates distribution of process gases provided from the body  102  to, for example, a processing volume of a process chamber via a plurality of gas distribution holes  142  formed in the gas distribution plate  104 . The gas distribution holes  142  may be arranged in any manner suitable to provide a desired distribution of process gases. For example, in some embodiments, the gas distribution holes  142  may be arranged in clusters disposed about the through holes  116  of the body  102  when the gas distribution plate  104  is coupled to the body  102 . 
     The gas distribution plate  104  may be fabricated from any material suitable to resist degradation during exposure to a plasma (e.g., a plasma formed in a process chamber during processing). For example in some embodiments, the gas distribution plate  104  may be fabricated from single crystalline silicon (Si). Single crystal silicon is not typically used as a material for the gas distribution plate at least in part due to single crystal silicon having a faster etch rate as compared to silicon carbide, a favored material. However, the inventors have observed that single crystalline silicon is less susceptible to surface roughness change, arcing, and micro-masking, and further provides better operability at elevated temperatures (e.g., higher than about 150 degrees Celsius) as compared to conventional materials utilized to fabricate gas distribution plates, for example, such as silicon carbide (SiC). In addition, single crystal silicon is more readily available and obtainable at a lower cost as compared to the conventional materials. In addition, in embodiments where the showerhead  100  is used in substrate processes involving silicon-containing gases, fabricating the gas distribution plate  104  from silicon reduces the instances of contamination due to degradation of the gas distribution plate  104 . 
     In some embodiments, the gas distribution plate  104  is fabricated from a single crystalline silicon material having a high electrical resistivity between about 60 ohm-cm and 90 ohm-cm to reduce arcing. As noted above, the inventors have observed that low resistivity gas distribution plates (e.g., a gas distribution plate having a resistivity of about 0.005-0.015 Ohm-cm) will arc during processes in which the source power is greater than or equal to 2000 watts at 162 MHz. Thus, the high resistivity of the gas distribution plate  104  advantageously reduces arcing when the showerhead  100  is used in high source power processes. In some embodiments, the ingot from which the single crystalline silicon is obtained may be doped to change the resistivity of the ingot. For example, the single crystalline silicon ingot may be doped or coated with a high resistivity material such as boron to increase the resistivity of the material. In some embodiments, if the gas distribution plate  104  is formed from a low resistivity material, the gas distribution plate  104  may be treated, coated or doped with a high resistivity material to increase the resistivity of the gas distribution plate  104 . 
     The gas distribution plate  104  may have any suitable thickness sufficient to provide a desired gas distribution and suitable useful functional life. In addition, in some embodiments, the gas distribution plate  104  may have a suitable thickness sufficient to ensure continuous contact with one or more thermal gaskets (three thermal gaskets  120 ,  122 ,  124  shown) disposed between the gas distribution plate  104  and the body  102  when the gas distribution plate  104  is coupled to the body  102 . For example, in some embodiments, the thickness of the gas distribution plate  104  may be selected such that an amount of bowing of the gas distribution plate  104  caused by the forces provided by the clamp  110  at the edge of the gas distribution plate  104  is less than an amount of deformation of the thermal gaskets  120 ,  122 ,  124  when compressed, thus ensuring continuous contact with each of the thermal gaskets  120 ,  122 ,  124  when clamped. Alternatively, or in combination, in some embodiments, the thickness of the gas distribution plate  104  may be selected to provide an aspect ratio of the gas distribution holes  142  suitable to reduce plasma penetration and improve the useful functional life of the gas distribution plate  104 . For example, in embodiments where the gas distribution holes  142  have a diameter of about 0.5 mm, the gas distribution plate  104  may have a thickness of about 9 mm. 
     The clamp  110  facilitates coupling the gas distribution plate  104  to the body  102 . In some embodiments, the clamp  110  facilities such coupling via a fastener  106  provided to a through hole  136  formed in the body  102  corresponding to a threaded hole  138  formed in the clamp. The clamp  110  may be fabricated from any process compatible conductive material, for example aluminum. In some embodiments, the clamp  110  may be coated with a spray coating (e.g., yttria (Y 2 O 3 )) to reduce degradation of the clamp  110  in a plasma environment. In some embodiments, the clamp  110  may alternatively be anodized with an aluminum oxide coating. 
     In some embodiments, the clamp  110  may include one or more channels formed in surfaces of the clamp  110  to accommodate one or more O-rings and RF gaskets (O-ring  128  and RF gasket  148  shown). When present, the O-ring  128  provides cushioning to the gas distribution plate  104  to prevent breakage of the gas distribution plate  104  when clamped to the body  102 . When present, the RF gasket  148  facilitates conductivity of RF power from the body  102 , through the clamp  110 , and to the gas distribution plate  104 , thus allowing the gas distribution plate  104  to function as an RF electrode. Providing the RF current path to the gas distribution plate  104  also shields a gap  146  between the body  102  and the gas distribution plate  104 , which reduces arcing, for example, at the through holes  116  of the body  102 . The O-ring  128  and RF gasket  148  may be fabricated from any suitable material, for example such as the materials discussed above with respect to the O-rings  130 ,  132 ,  134 , and RF gaskets  108 ,  126 . 
     In some embodiments, the thermal gaskets  120 ,  122 ,  124  may be disposed between the body  102  and gas distribution plate  104 . When present, the thermal gaskets  120 ,  122 ,  124  may facilitate a heat exchange between the body  102  and the gas distribution plate  104 , for example, to provide a more uniform thermal gradient across the gas distribution plate  104 . In addition, the thermal gaskets  120 ,  122 ,  124  may provide the gap  146  between the body  102  and the gas distribution plate  104  and define separate plenums (e.g., zones) for groups of through holes  116  and corresponding gas distribution holes  142 . In some embodiments, the showerhead  100  may also include a plurality of pins  152  that are pressed into the body  102 . The plurality of pins  152  ensures that the gap  146  remains substantially unchanged when the gas distribution plate  104  deflects toward the body  102 . The pins  152  each include a through-hole  153  to ensure that any gaps behind the pins  152  are properly evacuated. 
     The thermal gaskets  120 ,  122 ,  124  may be fabricated from any compressible, thermally conductive material having low out-gassing at process pressures and temperatures (e.g., vacuum conditions and temperatures at or above about 150 degrees Celsius). In some embodiments, the gasket may comprise a silicone containing material such as, for example, SARCON® GR-M available from Fujipoly® or other silicone rubber material having a high thermal conductivity and flame-retardant properties. The thermal gaskets  120 ,  122 ,  124  may have any shape suitable to maintain contact between the body  102  and the gas distribution plate  104 . For example, in some embodiments, the thermal gaskets  120 ,  122 ,  124  may be a plurality of concentric rings having a rectangular cross section as shown in  FIG. 1 . In some embodiments, the geometry of the thermal gaskets  120 ,  122 ,  124  may be optimized to accommodate for a difference in distance between the body  102  and the gas distribution plate  104  when clamped together due to the forces provided by the clamp  110  at the edge of the gas distribution plate  104  (e.g., bowing of the gas distribution plate  104 ). 
     In some embodiments, a protective ring  112  may be disposed about the showerhead to shield portions of the body  102 , clamp  110  and gas distribution plate  104 . The protective ring  112  may be fabricated from any suitable process compatible material, for example, quartz (SiO 2 ). 
       FIG. 2  depicts a schematic view of an illustrative process chamber  200  suitable for use with a showerhead in accordance with some embodiments of the present disclosure. Exemplary process chambers may include the ENABLER®, ENABLER® E5, ADVANTEDGE™, or other process chambers, available from Applied Materials, Inc. of Santa Clara, Calif. Other suitable process chambers having, or being modified to have, showerheads may similarly benefit from the present disclosure. 
     In some embodiments, the process chamber  200  may generally comprise a chamber body  202  having a substrate support pedestal  208  for supporting a substrate  210  thereupon disposed within an inner volume  205  of the chamber body, and an exhaust system  220  for removing excess process gases, processing by-products, or the like, from the inner volume  205  of the chamber body  202 . 
     In some embodiments, an upper liner  264  and a lower liner  266  may cover the interior of the chamber body  202  to protect the chamber body  202  during processing. In some embodiments, the chamber body  202  has an inner volume  205  that may include a processing volume  204 . The processing volume  204  may be defined, for example, between the substrate support pedestal  208  and a showerhead  214  (e.g., showerhead  100  described above) and/or nozzles provided at desired locations. In some embodiments, a gas supply  288  may provide one or more process gases to the showerhead  214  for distribution of the one or more process gases to the processing volume  204  of the chamber body  202 . 
     In some embodiments, the substrate support pedestal  208  may include a mechanism that retains or supports the substrate  210  on the surface of the substrate support pedestal  208 , such as an electrostatic chuck, a vacuum chuck, a substrate retaining clamp, or the like. Alternatively, or in combination, in some embodiments, the substrate support pedestal  208  may include mechanisms for controlling the substrate temperature (such as heating and/or cooling devices, not shown) and/or for controlling the species flux and/or ion energy proximate the substrate surface. For example, in some embodiments, the substrate support pedestal  208  may include an electrode  240  and one or more power sources (two bias power sources  238 ,  244 ) coupled to the electrode  240  via respective matching networks  236 ,  262 . For example, the substrate support pedestal  208  may be configured as a cathode coupled to a bias power source  244  via a matching network  262 . The above described bias power sources (e.g., bias power sources  238 ,  244 ) may be capable of producing up to 12,000 W at a frequency of about 2 MHz, or about 13.56 MHz, or about 60 Mhz. The at least one bias power source may provide either continuous or pulsed power. In some embodiments, the bias power source alternatively may be a DC or pulsed DC source. 
     In some embodiments, the substrate support pedestal  208  may include a substrate support ring  280  disposed atop the substrate support pedestal  208  and configured to support at least a portion of the substrate  210  during processing. In some embodiments, one or more rings (insert ring  278  and barrier ring  242  shown) may be disposed about the substrate support pedestal  208 . The one or more rings may be fabricated from any suitable process compatible material. For example, in some embodiments, the insert ring may be fabricated from silicon (Si). In some embodiments, the barrier ring  242  may be fabricated from quartz (SiO 2 ). In some embodiments, a grounded mesh  260  may be disposed about the periphery of the substrate support pedestal  208  and coupled to the chamber body  202 . 
     The substrate  210  may enter the chamber body  202  via an opening  212  in a wall of the chamber body  202 . The opening  212  may be selectively sealed via a slit valve  218 , or other mechanism for selectively providing access to the interior of the chamber through the opening  212 . The substrate support pedestal  208  may be coupled to a lift mechanism  234  that may control the position of the substrate support pedestal  208  between a lower position (as shown) suitable for transferring substrates into and out of the chamber via the opening  212  and a selectable upper position suitable for processing. The process position may be selected to maximize process uniformity for a particular process. When in at least one of the elevated processing positions, the substrate support pedestal  208  may be disposed above the opening  212  to provide a symmetrical processing region. 
     In some embodiments, a protective ring  206  (e.g., the protective ring  112  described above) may be disposed about, and covering at least a portion of, the showerhead  214 , for example, such as the body  294  (e.g., body  102  described above) or the gas distribution plate  296  (e.g., the gas distribution plate  104  described above) of the showerhead  214 . In some embodiments, the protective ring  206  may be supported by the upper liner  264 . 
     In some embodiments, the showerhead  214  may be coupled to and/or supported by, a chiller plate  270 . When present, the chiller plate  270  facilitates control over a temperature of the showerhead  214  during processing. In some embodiments, the chiller plate  270  comprises a plurality of channels (not shown) formed in the chiller plate  270  to allow a temperature control fluid provided by a temperature control fluid supply (chiller)  290  to flow through the chiller plate  270  to facilitate the control over the temperature of the showerhead  214 . 
     In some embodiments, one or more coils (inner coil  274  and outer coil  272  shown) may be disposed above and/or proximate a peripheral edge of the showerhead  214 . When present, the one or more coils may facilitate shaping a plasma formed within the processing volume  204  of the process chamber  200 . 
     In some embodiments, an RF power source  286  provides RF power to the chiller plate  270  and/or the showerhead  214  via a coaxial stub  292 . The RF power source  286  may operate at a power greater than or equal to 2000 Watts and a frequency of 162 MHz and up to 5000 W at a frequency of about 227 MHz. As described above, the inventive gas distribution plate  104  will not arc during processes in which the RF power source operates at a power of 2000 W or more at high frequencies. The coaxial stub  292  is a fixed impedance matching network having a characteristic impedance, resonance frequency, and provides an approximate impedance match between the showerhead  214  and the RF power source  286 . In some embodiments, the coaxial stub  292  generally comprises an inner cylindrical conductor  298 , an outer cylindrical conductor  201  and an insulator  203  filling the space between the inner cylindrical conductor  298  and the outer cylindrical conductor  201 . 
     The inner cylindrical conductor  298  and the outer cylindrical conductor  201  may be constructive of any suitable conductive material capable of withstanding the particular process environment. For example, in some embodiments, the inner cylindrical conductor  298  and the outer cylindrical conductor  201  may be fabricated from nickel-coated aluminum. One or more taps  221  are provided at particular points along the axial length of the coaxial stub  292  for applying RF power from the RF power source  286  to the coaxial stub  292 . An RF power terminal  207  and the RF return terminal  209  of the RF power source  286  are connected at the tap  221  on the coaxial stub  292  to the inner cylindrical conductor  298  and the outer cylindrical conductor  201 , respectively. A terminating conductor  211  at the far end  213  of the coaxial stub  292  shorts the inner cylindrical conductor  298  and the outer cylindrical conductor  201  together, so that the coaxial stub  292  is shorted at a far end  213  of the coaxial stub  292 . At the near end  215  of the coaxial stub  292 , the outer cylindrical conductor  201  is connected to the chamber body  202  via an annular conductive housing or support  276 , while the inner cylindrical conductor  298  is connected to the chiller plate  270  and/or showerhead  214  via a conductive cylinder  217 . In some embodiments, a dielectric ring  219 , is disposed between and separates the conductive cylinder  217  and the chiller plate  270 . 
     The exhaust system  220  generally includes a pumping plenum  224  and one or more conduits that couple the pumping plenum  224  to the inner volume  205  (and generally, the processing volume  204 ) of the chamber body  202 , for example via one or more inlets  222 . A vacuum pump  228  may be coupled to the pumping plenum  224  via a pumping port  226  for pumping out the exhaust gases from the chamber body  202 . The vacuum pump  228  may be fluidly coupled to an exhaust outlet  232  for routing the exhaust to appropriate exhaust handling equipment. A valve  230  (such as a gate valve, or the like) may be disposed in the pumping plenum  224  to facilitate control of the flow rate of the exhaust gases in combination with the operation of the vacuum pump  228 . Although a z-motion gate valve is shown, any suitable, process compatible valve for controlling the flow of the exhaust may be utilized. 
     To facilitate control of the process chamber  200  as described above, the controller  250  may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer-readable medium,  256  of the CPU  252  may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits  254  are coupled to the CPU  252  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. 
     One or more methods and/or processes may generally be stored in the memory  256  as a software routine  258  that, when executed by the CPU  252 , causes the process chamber  200  to perform the processes methods and/or processes. The software routine  258  may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU  252 . Some or all of the method of the present disclosure may also be performed in hardware. As such, the methods and/or processes may be implemented in software and executed using a computer system, in hardware as, e.g., an application specific integrated circuit or other type of hardware implementation, or as a combination of software and hardware. The software routine  258  may be executed after the substrate  210  is positioned on the substrate support pedestal  208 . The software routine  258 , when executed by the CPU  252 , transforms the general purpose computer into a specific purpose computer (controller)  250  that controls the chamber operation such that the methods disclosed herein are performed. 
     Thus, embodiments of a showerhead having a detachable gas distribution plate have been provided herein. Embodiments of the inventive showerhead may advantageously provide a longer useful life and a more cost efficient manner of replacing the gas distribution plate as compared to conventional showerheads. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.