Patent Publication Number: US-10770328-B2

Title: Substrate support with symmetrical feed structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 14/840,204, filed Aug. 31, 2015 which is also a continuation of co-pending U.S. patent application Ser. No. 12/910,547, filed Oct. 22, 2010, which is herein incorporated by reference. 
    
    
     FIELD 
     Embodiments of the present invention generally relate to substrate processing equipment. 
     BACKGROUND 
     As the critical dimensions of devices continue to shrink, factors that may have been irrelevant or of lesser import at large dimensions can become critical at smaller dimensions. 
     The inventors have provided an improved apparatus that may facilitate improved processing results when processing substrates. 
     SUMMARY 
     Apparatus for processing a substrate is disclosed herein. In some embodiments, a substrate support may include a substrate support having a support surface for supporting a substrate the substrate support having a central axis; a first electrode disposed within the substrate support to provide RF power to a substrate when disposed on the support surface; an inner conductor coupled to the first electrode about a center of a surface of the first electrode opposing the support surface, wherein the inner conductor is tubular and extends from the first electrode parallel to and about the central axis in a direction away from the support surface of the substrate support; an outer conductor disposed about the inner conductor; and an outer dielectric layer disposed between the inner and outer conductors, the outer dielectric layer electrically isolating the outer conductor from the inner conductor. In some embodiments, the outer conductor may be coupled to an electrical ground. In some embodiments DC energy may be provided to a second electrode via a second conductor extending along the central axis. In some embodiments, AC energy may be provided to one or more heater electrodes via a plurality of third conductors disposed symmetrically about the central axis. In some embodiments, the second and third conductors may be disposed within an axial opening of the inner conductor. 
     In some embodiments, a plasma processing apparatus may include a process chamber having an inner volume with a substrate support disposed in the inner volume, the substrate support having a support surface and a central axis; a first electrode disposed in the substrate support to provide RF power to a substrate when present on the substrate support; an inner conductor having a first end coupled to the first electrode about a center of a surface of the first electrode facing away from the support surface, wherein the inner conductor is tubular and extends away from the first electrode parallel to and about the central axis; a first conductor coupled to the inner conductor proximate a second end of the inner conductor, opposite the first end, the first conductor extending laterally from the central axis toward an RF power source disposed off-axis from the central axis, the RF power source to provide RF power to the first electrode; an outer conductor disposed about the inner conductor; and an outer dielectric layer disposed between the inner and outer conductors, the outer dielectric layer electrically isolating the outer conductor from the inner conductor. 
     Other and further embodiments of the present invention are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the invention depicted in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  depicts schematic side view of a process chamber in accordance with some embodiments of the present invention. 
         FIG. 2  depicts a schematic side view of substrate support in accordance with some embodiments of the present invention. 
         FIG. 3  depicts a top cross sectional view of a plurality of conductors arranged about a central axis in accordance with some embodiments of the present invention. 
         FIG. 4  depicts a schematic side view of mechanisms coupled to a substrate support in accordance with some embodiments of the present invention. 
     
    
    
     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. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Apparatus for processing a substrate is disclosed herein. The inventors have discovered that a substrate support having an asymmetric electrical feed structure to provide electrical power to an electrode disposed in the substrate support can cause process non-uniformities, for example, such as etch rate and etch dimension non-uniformities on a substrate disposed atop the substrate support. Thus, the inventors have provided a symmetrical electrical feed structure that may be incorporated within a substrate support to advantageously improve etch rate and/or etch dimension uniformities. In some embodiments, the inventive apparatus may advantageously reduce electromagnetic skew along the surface of a substrate by conducting electrical power to the various components of the substrate support via one or more conductors that are symmetrically arranged with respect to a central axis of the substrate support and/or by providing one or more elements for confining or uniformly distributing an electric and/or magnetic field. 
       FIG. 1  depicts a schematic diagram of an illustrative etch reactor  100  of the kind that may be used to practice embodiments of the invention as discussed herein. The reactor  100  may be utilized alone or, more typically, as a processing module of an integrated semiconductor substrate processing system, or cluster tool, such as a CENTURA® integrated semiconductor substrate processing system, available from Applied Materials, Inc. of Santa Clara, Calif. Examples of suitable etch reactors  100  include the ADVANTEDGE™ line of etch reactors (such as the AdvantEdge S or the AdvantEdge HT), the DPS® line of etch reactors (such as the DPS®, DPS® II, DPS® AE, DPS® HT, DPS® G3 poly etcher), or other etch reactors, available from Applied Materials, Inc. Other etch reactors and/or cluster tools, including those of other manufacturers may be used as well. 
     The reactor  100  comprises a process chamber  110  having a substrate support  116  disposed within a processing volume  117  formed within a conductive body (wall)  130 , and a controller  140 . A symmetric electrical feed through  150  may be provided to coupled electrical energy to one or more electrodes disposed within the substrate support  116 , as discussed below. The chamber  110  may be supplied with a substantially flat dielectric ceiling  120 . Alternatively, the chamber  110  may have other types of ceilings, e.g., a dome-shaped ceiling. An antenna comprising at least one inductive coil element  312  is disposed above the ceiling  120  (two co-axial elements  112  are shown). The inductive coil element  112  is coupled to a plasma power source  118  through a first matching network  119 . The plasma power source  118  typically may be capable of producing up to 3000 W at a tunable frequency in a range from 50 kHz to 13.56 MHz. 
     As illustrated in  FIG. 1 , the substrate support  116  may include a plurality of components, such as electrodes, heaters, and the like, which may operated by one or more mechanisms  148  disposed below the substrate support  116 . For example, and as shown in  FIG. 1 , the one or more mechanisms may be coupled to the substrate support  116  through an opening  115  disposed through the conductive body (wall  130 ). A bellows  152  may be provided to facilitate maintaining a seal between the interior of the process chamber and the outside of the process chamber while allowing the substrate support to move relative to the process chamber. For example, the bellows  152  may compress or expand as the substrate support  116  is raised or lowered within the processing volume  117 . The one or more mechanisms  148  may include a lift mechanism  154  that may be utilized to raise and lower the substrate support  116  relative to one or more plasma generating elements, such as the inductive coil elements  112 , disposed above the substrate support  116 . The one or more mechanisms  148  are described in further detail below and with respect to  FIG. 4 . 
       FIG. 2  depicts a schematic side view of the substrate support  116  and symmetric electrical feed structure  150  in accordance with some embodiments of the present invention. As illustrated in  FIG. 2 , the substrate support may include a base  200  having a central opening  202 . The central opening  202  may be utilized, for example, to provide one or more conductors therethrough to couple one or more of radio frequency (RF), alternating current (AC), or direct current (DC) power from the one or more mechanisms  148  disposed below the substrate support  116 . The base  200  may have a protruding portion  204  to facilitate coupling the base  200  to other components of the process chamber. 
     The substrate support  116  may include a first electrode  206  disposed within the substrate support  116  to provide RF power to a substrate, such as the substrate  114  (shown in  FIG. 1 ), when disposed on the substrate support  116 . The first electrode  206  may include a central axis  208 . An inner conductor  210  may be coupled to the first electrode  206 . The inner conductor  210  may be a cylindrical tube having a central axis aligned with the central axis  208  such that the inner conductor  210  may provide RF energy to the first electrode  206  in a symmetrical manner. The inner conductor  210  generally extends away from the first electrode  206  parallel to and about the central axis  208 . The inner conductor  210  may extend through the central opening  202  in the base  200  (as shown), through the bellows  152  (shown in  FIG. 1 ), and into the one or more mechanisms  148  (as illustrated in  FIG. 4 , described below). The inner conductor  210  may comprise any suitable conducting material, such as copper (Cu), aluminum (Al), gold-plated copper, or the like. In some embodiments, the inner conductor may comprise copper. 
     The substrate support  116  further includes an outer conductor  212  disposed about at least portions of the inner conductor  210 . The outer conductor  212 , similar to the inner conductor  210 , may be tubular in shape and extend generally parallel to and about the central axis  208 . The outer conductor  212  may comprise any suitable conducting material, such as aluminum (Al), copper (Cu), or the like. In some embodiments, the outer conductor  212  may comprise Al. The outer conductor  212  may extend away from a conductive plate  214  disposed above the base  200 . The outer conductor  212  may be coupled to an electrical ground, such as by having an opposing end of the outer conductor  212  coupled to a case  400  which contains the one or more mechanisms  148  as shown in  FIG. 4  and described below. Alternatively, the outer conductor  212  may be separately grounded (not shown). 
     An outer dielectric layer  216  may be disposed between the inner and outer conductors  210 ,  212  to electrically isolate the outer conductor  212  from the inner conductor  210 . The outer dielectric layer  216  may comprise any suitable dielectric material, such as a polytetrafluoroethylene (PTFE)-containing material, such as TEFLON® (available from DuPont of Wilmington, Del.), or the like. In some embodiments, the outer dielectric layer  216  may comprise PTFE. In operation, electrical energy, such as RF energy, may flow through the inner conductor  210  to the first electrode  206 . An electric field may typically exist between the inner conductor  210  and any other conductive element proximate the inner conductor  210 . Further, a magnetic field may be induced by the electrical current flowing through the inner conductor  210 . The outer conductor  212  may act to confine the electric and magnetic fields to the region between the inner and outer conductor  210 ,  212 , e.g., to the region which includes the outer dielectric layer  216 . The confinement of the electric and magnetic fields to this region may result in improved uniformity in the distribution of the electric and magnetic fields, which can result in improved etch rate and etch dimension uniformity on the substrate  114  disposed atop the substrate support  116 . Further the conductive plate  214  may similarly act to confine the electric and magnetic fields and/or symmetrically distribute the electric and magnetic fields about the conductive plate  214 . Additionally, the conductive plate  214  may act as a shield to isolate the substrate  114  from asymmetric electric and magnetic fields caused by other components, such as a first conductor  408  illustrated in  FIG. 4 , described below. 
     The substrate support  116  may further include a dielectric layer  218  disposed between the first electrode  206  and the conductive plate  214 . The dielectric layer  218  may comprise a process compatible dielectric material, such as Rexolite®, a cross-linked polystyrene, available from C-Lec Plastics, Inc. of Philadelphia, Pa., or the like. The dielectric layer  218  may be utilized to limit power losses, for example, between the first electrode  206  and the conductive plate  214 . 
     In some embodiments, the substrate support  116  may include an electrostatic chuck (ESC)  220  disposed above the first electrode  206 . The ESC may generally comprise a base layer  226  having a dielectric layer  248  disposed over the base layer  226 . The base layer  226  may be a cooling plate to facilitate keeping the electrostatic chuck  220  at a desired temperature during operation. For example, the base layer  226  may comprise a highly heat conductive material, such as aluminum or copper, and may have one or more channels for flowing a heat transfer fluid through the channels. 
     The ESC  220  may include a second electrode  222 . In some embodiments the second electrode  222  may be disposed within the dielectric layer  248 . The second electrode  222  may be coupled to a source of DC energy to electrostatically secure the substrate  114  to the substrate support  116  via a second conductor  236 . In some embodiments, the second conductor  236  may be disposed along the central axis  208  and within the axial opening of the inner conductor  210  in order to minimize any RF interference from the DC energy being provided and to make any such RF interference symmetrical. In some embodiments, the second conductor  236  may be a conductive rod. The second conductor  236  may be fabricated from any suitable process-compatible conductive material. In some embodiments, the second conductor  236  comprises copper. 
     In some embodiments, the ESC  220  may further include one or more heater electrodes  238 . In some embodiments the one or more heater electrodes  238  may be disposed within the dielectric layer  248 . The one or more heater electrodes  238  may be provided in any suitable pattern and may be arranged in one or more heater zones to provide a desired heating pattern for heating the substrate. The one or more heater electrodes  238  may be coupled to a source of AC energy via a plurality of third conductors  234 . Application of AC energy to the one or more heater electrodes  238  causes the electrodes to heat up by resistive heating (i.e., Joule heating). In some embodiments, the third conductors  234  may be conductive rods. The third conductors  234  may be fabricated from any suitable process-compatible conductive material. In some embodiments, the third conductors  234  comprise copper. 
     In some embodiments, an electrical distribution plate  240  may be provided to route the connections from the plurality of third conductors  234  to the one or more heater electrodes  238 . For example, in some embodiments, the electrical distribution plate  240  may include a printed circuit board (PCB)  242 , or the like, for connecting to the plurality of third conductors  234  and for providing conductive paths (e.g., electrical traces) to a plurality of AC terminals  224 . An AC terminal insulator plate  244  may be disposed over the PCB  242  to insulate the conductive paths and the AC terminals  224  from adjacent conductive elements, such as the base layer  226  of the ESC  220 . Conductors  246  may be provided to couple the AC terminals  224  to respective ones of the plurality of third conductors  234 . In some embodiments, the conductors  246  may be conductive rods. In some embodiments, the conductors  246  may comprise copper. 
     In some embodiments, the third conductors  234  may be symmetrically disposed about the central axis  208 . In some embodiments, the third conductors  234  may be symmetrically disposed about the central axis  208  and may be disposed within the axial opening of the inner conductor  210  (as shown). In some embodiments, the AC terminals  224  may be symmetrically disposed about the central axis  208 , for example, having each AC terminal  224  in alignment with a respective one of the plurality of third conductors  234 . The inventors have found that the symmetrical arrangement of the third conductors  234  about the central axis  208  can further minimize RF interference and improve process performance, such as improving etch rate uniformity and/or etch dimension uniformity on a substrate. 
     In some embodiments, the second conductor  236  and the plurality of third conductors  234  may be routed through the open central portion of the inner conductor  210 . An inner dielectric layer  228  may be disposed within the inner conductor  210  and may have the second conductor  236  and the plurality of third conductors  234  routed through passages disposed through the inner dielectric layer  228 . The passages of the inner dielectric layer  228  may insulate the second conductor  236  and the plurality of third conductors  234  from each other, from the inner conductor  210 , and from other adjacent electrically conductive components or layers. The passages of the inner dielectric layer  228  may further position the second conductor  236  and the plurality of third conductors  234  in a desired location or pattern, such as a symmetric pattern. The inner dielectric layer  228  may comprise similar dielectric materials as discussed above for the outer dielectric layer  216 . 
     The inner dielectric layer  228 , as shown in  FIG. 2  and in top cross sectional view in  FIG. 3 , is generally disposed within the inner conductor  210 , but may extend beyond the end of the inner conductor  210  to surround at least a portion of the lengths of the second conductor  236  and the plurality of third conductors  234  that extend beyond the end of the inner conductor  210 . For example, the inner dielectric layer  228  may include a first portion  230  surrounding a portion of the plurality of third conductors  234  that extend past the end of the inner conductor  210  toward the electrical distribution plate  242 . A second portion  232  may surround a portion of the second conductor  236  that extends past the end of the inner conductor  210  toward the second electrode  222 . 
       FIG. 3  illustrates a schematic partial top view of the symmetric electrical feed structure  150  in accordance with at least some embodiments of the present invention. As shown in  FIG. 3 , the symmetric electrical feed structure  150  includes the inner conductor  210  and the outer conductor  216  separated by the outer dielectric layer  216 . The inner dielectric layer  228  insulates and positions the second conductor  236  and the plurality of third conductors  234  in a desired pattern (e.g., symmetrically). For example, the second conductor  236  may be centrally disposed in the inner dielectric layer  228  along the central axis  208  and the plurality of third conductors  234  may be disposed symmetrically about the central axis  208 . 
       FIG. 4  depicts a schematic side view of a lower portion of the symmetric electrical feed structure  150  showing the one or more mechanisms  148  coupled to the substrate support  116  in accordance with at least some embodiments of the present invention. As shown in  FIG. 4 , the lower portion of the symmetric electrical feed structure  150  may provide for the connection to a source of RF energy and optionally, one or more of AC or DC energy. For example, the inner conductor  210  may be coupled to an RF power source  406 , for example, via a first conductor  408 , to provide RF energy to the first electrode  206  via the first conductor  408 . In some embodiments, the second conductor  236  may be coupled to a DC power source  402  to provide DC energy to the second electrode  222  to electrostatically retain a substrate on the substrate support  116 . In some embodiments, the plurality of third conductors  234  may be coupled to an AC power supply  404  to provide AC energy to the electrodes  238  to provide heat to the substrate. 
     The first conductor  408  may be coupled to the inner conductor  210  about the outer surface of the inner conductor  210  to provide the RF energy symmetrically to the inner conductor  210 . The first conductor  408  may extend laterally from the central axis  208  toward the RF power source  406 , which may be disposed to the side of the central axis  208 . The RF power source  406  may be coupled to the first conductor  408  via a match network  410 . The RF power source  406  may provide RF energy at any suitable frequency and power for a particular application. In some embodiments, the RF power source  406  may be capable of providing up to about 1500 W of RF energy at a frequency of about 13.56 MHz. The RF power may be provided either in a continuous wave or pulsed mode. 
     In some embodiments, a second dielectric layer  414  may be provided to electrically isolate the first conductor  408  from adjacent electrically conductive components (such as a grounding case  400 , discussed below, that encloses the lower portion of the electrical feed structure  150 ). In some embodiments, and as shown in  FIG. 4 , the first conductor  408  may be embedded within the second dielectric layer  414 . 
     Although the first conductor  408  is disposed at an angle to the inner conductor  210 , which may result in a disturbance in the electromagnetic field created by the RF current, the conductive plate  214  may function to limit the electromagnetic effect caused by the orientation of the first conductor  408 . As such, any asymmetries in the electric field that might be generated due to the orientation of the first conductor should have limited or no affect on processes being performed on a substrate disposed on the substrate support  116 . 
     In some embodiments, a dielectric end cap  416  may be provided about the end of the RF feed structure  150 . For example, the dielectric end cap  416  may be placed about a portion of the inner dielectric layer  228  that extends beyond the inner conductor  210 . In some embodiments, the dielectric end cap  416  may cover a portion of the inner dielectric layer  228  that extends beyond the second dielectric layer  414 . The dielectric end cap  416  may have a plurality of openings to allow the conductors of the electrical feed structure  150  to extend therethrough. The conductors may be respectively coupled to the DC power supply  402  and/or the AC power supply  404  by respective conductive paths coupled to the plurality of conductors  234  and the conductor  236 . For example, a printed circuit board (PCB)  418  may be provided having electrical traces formed therein or thereon to route the plurality of conductors  234  to the AC power supply  404 . A separate conductive path may be provided to couple the conductor  236  to the DC power supply  402 . In some embodiments, a terminal  420  (shown in dotted lines) may be provided to facilitate coupling of the conductor  236  to the DC power supply  402 . The terminal  420  may extend through the entire PCB  418  or just a portion of the PCB  418 . In some embodiments, the PCB  418  may comprise a base  422 , a substrate  424  supported by the base  422 , and a cover  426 . The cover  426  may cover the substrate  424  and retain the substrate  424  between the base  422  and the cover  426 . Openings may be provided in the cover  426  to facilitate making electrical connections to the conductors  234 ,  236 , the terminal  420 , and/or any electrical traces in or on the substrate  424  or passing through the substrate  424 . 
     In some embodiments, a grounding case  400  may be provided to substantially enclose the lower portion of the symmetric electrical feed structure  150 , for example, in the region where RF energy is coupled to the inner conductor  210 . The grounding case  400  may include an opening  401  through which one or more components of the symmetric electrical feed structure  150 , such as the outer dielectric layer  216 , inner conductor  210 , inner dielectric layer  228 , second conductor  236 , and plurality of third conductors  234 , may be disposed. In some embodiments, and as shown in  FIG. 4 , an end of the bellows  152  and an end of the outer conductor  212  may be coupled to the grounding case  400  proximate the opening  401 . In some embodiments, the grounding case  400  may provide the electrical ground for the outer conductor  212 . 
     The grounding case  400  may also have an opening  403  to facilitate routing the second conductor  236  and the plurality of third conductors  234  to the respective DC and AC power sources. The inner dielectric layer  228  and/or the dielectric and  416  may electrically isolate the second and third conductors  234 ,  236  from the grounding case  400 , as shown. In some embodiments, additional conductors may be provided to respectively couple the second conductor  236  and the plurality of third conductors  234  to the DC power source  402  and the AC power supply  404 . 
     Returning to  FIG. 1 , the controller  140  comprises a central processing unit (CPU)  144 , a memory  142 , and support circuits  146  for the CPU  144  and facilitates control of the components of the chamber  110 . To facilitate control of the process chamber  110  as described above, the controller  140  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  142 , or computer-readable medium, of the CPU  144  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  146  are coupled to the CPU  144  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. The methods, such as etch process recipes or the like used to process the substrate  114  may be generally stored in the memory  142  as a software routine. The software routine 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  144 . 
     In operation, the substrate  114  is placed on the substrate support  116  and process gases are supplied from a gas panel  138  through entry ports  126  and form a gaseous mixture. The gaseous mixture is ignited into a plasma  155  in the chamber  110  by applying power from the plasma source  118  and RF power source  406  to the inductive coil element  312  and the first electrode  206 , respectively. The pressure within the interior of the chamber  110  is controlled using a throttle valve  127  and a vacuum pump  136 . Typically, the chamber wall  130  is coupled to an electrical ground  134 . The temperature of the wall  130  is controlled using liquid-containing conduits (not shown) that run through the wall  130 . 
     The temperature of the substrate  114  may be controlled by stabilizing a temperature of the substrate support  116 . In one embodiment (not shown), helium gas from a gas source may be provided via a gas conduit to channels (not shown) formed in the surface of the substrate support  116  under the substrate  114 . The helium gas may be used to facilitate heat transfer between the substrate support  116  and the substrate  114 . During processing, the substrate support  116  may be heated by a resistive heater, such as the plurality of AC terminals  224  discussed above, to a steady state temperature and then the helium gas facilitates uniform heating of the substrate  114 . Using such thermal control, the substrate  114  may be maintained at a temperature of about 0 to about 150 degrees Celsius. 
     Although described with respect to an inductively coupled plasma etch chamber, other etch chambers may be used to practice the invention, including chambers with remote plasma sources, electron cyclotron resonance (ECR) plasma chambers, and the like. In addition, other non-etch chambers that provide RF energy to an electrode disposed in a substrate support may also be modified in accordance with the teachings provided herein. 
     Thus, apparatus for processing a substrate has been disclosed herein. At least some embodiments of the inventive apparatus may include a symmetric electrical feed structure that may advantageously improve substrate processing, such as etch rate and/or etch dimension uniformities. The inventive symmetric electrical feed structure and substrate supports incorporating same may advantageously reduce electromagnetic skew along the surface of a substrate by conducting electrical power to the various components of the substrate support via one or more conductors that are symmetrically arranged with respect to a central axis of the substrate support and/or by providing one or more elements for confining or uniformly distributing an electric and/or magnetic field. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.