Patent Publication Number: US-11393710-B2

Title: Wafer edge ring lifting solution

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/287,038, filed on Jan. 26, 2016, and Indian Provisional Application No. 201641019009, filed on Jun. 2, 2016, each of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     Examples of the present disclosure generally relate to apparatuses for processing substrates, such as semiconductor substrates. More particularly, a process kit and methods for use thereof, are disclosed. 
     Description of the Related Art 
     In the processing of substrates, such as semiconductor substrates and display panels, a substrate is placed on a support in a process chamber while suitable process conditions are maintained in the process chamber to deposit, etch, form layers on, or otherwise treat surfaces of the substrate. During etching processes, a plasma, which drives the etching process, may not be uniformly distributed across the substrate surface. The non-uniformity is particularly apparent at the edge of the substrate surface. This non-uniformity contributes to poor processing results. Thus, some process chambers use edge rings, which may also be referred to as a process kit ring, in order to increase plasma uniformity and improve process yield. 
     However, traditional edge rings erode over time. As the edge ring erodes, plasma uniformity across the substrate surface decreases, thereby negatively affecting substrate processing. Since there is a direct correlation between plasma uniformity and the quality of processed substrates, traditional process chambers require frequent replacement of edge rings to maintain plasma uniformity. However, the frequent replacement of edge rings results in undesirable downtime for preventative maintenance, and leads to increased costs for consumable components such as the edge rings. 
     Therefore, there is a need in the art for methods and apparatuses that improve plasma uniformity. 
     SUMMARY 
     In one example, an apparatus for processing a substrate includes a substrate support, an electrostatic chuck disposed on the substrate support, and a process kit surrounding the electrostatic chuck. The electrostatic chuck includes a first portion, a second portion, and a third portion. The process kit includes a support ring disposed on a surface of the third portion of the electrostatic chuck, an edge ring independently moveable relative to the support ring disposed on a surface of the second portion of the electrostatic chuck, and a cover ring disposed on the support ring, wherein the cover ring has a first surface contacting the support ring. 
     In another example, a substrate support assembly includes an electrostatic chuck including a first portion having a first surface, a second portion having a second surface, and a third portion having a third surface and a process kit. The process kit includes a support ring disposed on the third surface of the third portion of the electrostatic chuck and surrounds the second portion of the electrostatic chuck, an edge ring disposed on the second surface of the second portion of the electrostatic chuck, and a cover ring disposed on the support ring, wherein the cover ring surrounds the edge ring. The substrate support assembly further includes one or more push pins positioned to elevate the edge ring, and one or more actuators coupled to the one or more push pins the one or more actuators are operable to control an elevation of the one or more push pins. 
     In another example, a method includes processing a first number of substrates while maintaining an edge ring in a first position in a process chamber, elevating the edge ring from the first position to a second position, and removing the edge ring from the process chamber by a robot after all of the first number of substrates have been removed from the process chamber. While processing a first substrate of the first number of substrates, the first substrate is disposed on a first surface of a first portion of an electrostatic chuck, the edge ring is disposed on a second surface of a second portion of the electrostatic chuck and is surrounded by a cover ring disposed on a support ring, and the support ring is disposed on a third surface of a third portion of the electrostatic chuck. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to aspects of the disclosure, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective aspects. 
         FIG. 1  is a schematic cross-sectional side view of a process chamber according to one example of the disclosure. 
         FIGS. 2A-2B  are enlarged schematic cross-sectional side views of a substrate support assembly of the process chamber of  FIG. 1  according to one example of the disclosure. 
         FIG. 3  is an enlarged schematic cross-sectional partial side view of a substrate support assembly according to another example of the disclosure. 
         FIG. 4  is an enlarged schematic cross-sectional partial side view of a substrate support assembly according to another example of the disclosure. 
         FIG. 5  is a flow chart of a method according to examples described herein. 
         FIGS. 6A-6C  schematically illustrate substrate surfaces at various stages of the method of  FIG. 5  according to examples of the disclosure. 
         FIG. 7  is a schematic cross-sectional partial side view of a substrate support assembly according to another example of the disclosure. 
         FIGS. 8A-8B  are schematic cross-sectional partial side views of the substrate support assembly of  FIG. 7  according to examples of the disclosure. 
         FIG. 9  is a schematic top view of the substrate support assembly of  FIG. 7  according to one example of the disclosure. 
         FIG. 10A  is a schematic top view of an edge ring according to one example of the disclosure. 
         FIG. 10B  is a schematic side view of a portion of the edge ring of  FIG. 10A  according to one example of the disclosure. 
         FIG. 11A  is a schematic top view of a support ring according to one example of the disclosure. 
         FIG. 11B  is an enlarged schematic top view of a portion of the support ring of  FIG. 11A  according to one example of the disclosure. 
         FIG. 12  is a schematic cross-sectional partial side view of a substrate support assembly according to another example of the disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the Figures. Additionally, elements of one example may be advantageously adapted for utilization in other examples described herein. 
     DETAILED DESCRIPTION 
     Apparatuses including a height-adjustable edge ring, and methods for use thereof are described herein. In one example, a substrate support assembly includes a height-adjustable edge ring, and the substrate support assembly is located within a process chamber. The substrate support assembly includes an electrostatic chuck, an edge ring positioned on a portion of the electrostatic chuck, and one or more actuators to adjust the height of the edge ring via one or more push pins. The height-adjustable edge ring can be used to compensate for erosion of the edge ring over time. In addition, the height-adjustable edge ring can be removed from the process chamber via a slit valve opening without venting and opening the process chamber. The height-adjustable edge ring can be tilted by the one or more actuators in order to improve azimuthal uniformity at the edge of the substrate. 
       FIG. 1  is a schematic sectional view of a process chamber  100 , according to one example of the disclosure. The process chamber  100  includes a chamber body  101  and a lid  103  disposed thereon that together define an inner volume. The chamber body  101  is typically coupled to an electrical ground  107 . A substrate support assembly  111  is disposed within the inner volume to support a substrate  109  thereon during processing. The process chamber  100  also includes an inductively coupled plasma apparatus  102  for generating a plasma within the process chamber  100 , and a controller  155  adapted to control examples of the process chamber  100 . 
     The substrate support assembly  111  includes one or more electrodes  153  coupled to a bias source  119  through a matching network  120  to facilitate biasing of the substrate  109  during processing. The bias source  119  may illustratively be a source of up to about 1000 W (but not limited to about 1000 W) of RF energy at a frequency of, for example, approximately 13.56 MHz, although other frequencies and powers may be provided as desired for particular applications. The bias source  119  may be capable of producing either or both of continuous or pulsed power. In some examples, the bias source  119  may be a DC or pulsed DC source. In some examples, the bias source  119  may be capable of providing multiple frequencies. The one or more electrodes  153  may be coupled to a chucking power source  160  to facilitate chucking of the substrate  109  during processing. The substrate support assembly  111  may include a process kit (not shown) surrounding the substrate  109 . Various embodiments of the process kit are described below. 
     The inductively coupled plasma apparatus  102  is disposed above the lid  103  and is configured to inductively couple RF power into the process chamber  100  to generate a plasma within the process chamber  100 . The inductively coupled plasma apparatus  102  includes first and second coils  110 ,  112 , disposed above the lid  103 . The relative position, ratio of diameters of each coil  110 ,  112 , and/or the number of turns in each coil  110 ,  112  can each be adjusted as desired to control the profile or density of the plasma being formed. Each of the first and second coils  110 ,  112  is coupled to an RF power supply  108  through a matching network  114  via an RF feed structure  106 . The RF power supply  108  may illustratively be capable of producing up to about 4000 W (but not limited to about 4000 W) at a tunable frequency in a range from 50 kHz to 13.56 MHz, although other frequencies and powers may be utilized as desired for particular applications. 
     In some examples, a power divider  105 , such as a dividing capacitor, may be provided between the RF feed structure  106  and the RF power supply  108  to control the relative quantity of RF power provided to the respective first and second coils. In some examples, the power divider  105  may be incorporated into the matching network  114 . 
     A heater element  113  may be disposed atop the lid  103  to facilitate heating the interior of the process chamber  100 . The heater element  113  may be disposed between the lid  103  and the first and second coils  110 ,  112 . In some examples, the heater element  113  may include a resistive heating element and may be coupled to a power supply  115 , such as an AC power supply, configured to provide sufficient energy to control the temperature of the heater element  113  within a desired range. 
     During operation, the substrate  109 , such as a semiconductor wafer or other substrate suitable for plasma processing, is placed on the substrate support assembly  111  and process gases supplied from a gas panel  116  through entry ports  117  into the inner volume of the chamber body  101 . The process gases are ignited into a plasma  118  in the process chamber  100  by applying power from the RF power supply  108  to the first and second coils  110 ,  112 . In some examples, power from a bias source  119 , such as an RF or DC source, may also be provided through a matching network  120  to electrodes  153  within the substrate support assembly  111 . The pressure within the interior of the process chamber  100  may be controlled using a valve  121  and a vacuum pump  122 . The temperature of the chamber body  101  may be controlled using liquid-containing conduits (not shown) that run through the chamber body  101 . 
     The process chamber  100  includes a controller  155  to control the operation of the process chamber  100  during processing. The controller  155  comprises a central processing unit (CPU)  123 , a memory  124 , and support circuits  125  for the CPU  123  and facilitates control of the components of the process chamber  100 . The controller  155  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  124  stores software (source or object code) that may be executed or invoked to control the operation of the process chamber  100  in the manner described herein. 
       FIGS. 2A and 2B  are enlarged schematic views of the substrate support assembly  111  of process chamber  100  according to one example described herein. The substrate support assembly  111  includes a process kit  203 , a substrate support  205 , and an electrostatic chuck  229 . The electrostatic chuck  229  is disposed on a top surface of the substrate support  205  and surrounded by the process kit  203 . The substrate support  205  includes a ground plate  226  surrounding an insulating plate  227 , and a facilities plate  228  assembled in a vertical stack. The substrate support  205  further includes a sleeve  230  circumscribing the facilities plate  228  and the electrostatic chuck  229  to insulate the RF hot electrostatic chuck  229  from the ground plate  226 . The sleeve  230  may be fabricated from quartz. The process kit  203  includes a cover ring  246 , a first edge ring  242 , and a second edge ring  244 . The cover ring  246  is positioned on an upper surface of the vertical edge of the ground plate  226  and includes a recess for engaging the sleeve  230 . The cover ring  246  may be fabricated from quartz or any other plasma-resistant material. 
     The facilities plate  228  is positioned above a lower portion of the ground plate  226  and between the insulating plate  227  and the electrostatic chuck  229 . The electrostatic chuck  229  may include a plurality of electrodes  153  (four are shown) embedded in an insulating material  236 . The electrodes  153  are coupled to the chucking power source  160  (shown in  FIG. 1 ) to facilitate chucking of a substrate  109  to an upper surface of the electrostatic chuck  229 . One or more heating or cooling channels may optionally be formed in the insulating material  236  to facilitate temperature control of the substrate  109  during processing. In some aspects, the electrodes  153  are cathodes coupled through the matching network  120  to the bias source  119  (shown in  FIG. 1 ). 
     The first edge ring  242  is positioned on the electrostatic chuck  229 . The first edge ring  242  surrounds and abuts the radially-outward edges of the substrate  109 . The first edge ring  242  facilitates protection of the edges of the substrate  109  during processing, and additionally, provides lateral support to the substrate  109  during processing. The first edge ring  242  may be stationary with respect to the substrate  109  during processing. 
     The second edge ring  244  is positioned over and radially outward of the first edge ring  242 . The radially-outward edge  202  of the second edge ring  244 , as well as a bottom surface  204  of the second edge ring  244 , is in contact with a cover ring  246 . The second edge ring  244  is positioned concentrically with respect to the first edge ring  242  and the substrate  109 . The second edge ring  244  assists the first edge ring  242  in providing the substrate  109  with lateral support and reducing undesired etching or deposition of material at the radially-outward edges of the substrate  109 . 
     The substrate support assembly  111  may also include one or more actuators  247  (one is shown), such as a stepper motor or linear actuator, among others. In one example, the one or more actuators  247  are disposed in the ground plate  226 . It is contemplated, however, that the actuator  247  may be positioned externally of the substrate support assembly  111 . Each actuator  247  is adapted to engage, or interface with, one or more push pins  248 . The one or more push pins  248  extend from the ground plate  226 , through the facilities plate  228  and the sleeve  230 , and into contact with the cover ring  246 . Actuation of the one or more push pins  248  results in vertical actuation, or displacing, of the cover ring  246  and the second edge ring  244  relative to an upper surface of the substrate  109  and/or the first edge ring  242 . It is contemplated that the first edge ring  242  may be omitted in some aspects. The position of the second edge ring  244  may be adjusted to a height which accommodates for erosion of the second edge ring  244  in order to increase plasma uniformity across a substrate surface during processing. 
     One or more bellows (shown in  FIG. 7 ) may be positioned around each of the one or more push pins  248  to reduce particle contamination within the process chamber  100  (shown in  FIG. 1 ). Additionally, one or more push pin guides  239 , such as a guide sleeve or bearing, may be positioned in the sleeve  230  around each push pin  248  to facilitate actuation of each push pin  248 . The push pin guides  239  provide bearing surfaces for push pins  248 . In one example, the one or more actuators  247 , the one or more push pins  248 , the cover ring  246  and the second edge ring  244  may be referred to as a height-adjustable edge ring assembly  249 . In one example, the edge ring assembly  249  may further interface and be operably controlled by the controller  155  (shown in  FIG. 1 ). In another example, the edge ring assembly  249  may omit the cover ring  246 . In such an example, the one or more push pins  248  may directly contact and actuate the second edge ring  244 . 
     In one example, the first edge ring  242  may be fabricated from silicon. In one example, the second edge ring  244  may be fabricated from silicon. In a particular example, the second edge ring  244  may be fabricated from silicon carbide (SiC). In one example, the one or more actuators  247  are micro-stepper motors. In another example, the one or more actuators  247  are piezo-electric motors. In one example, the one or more push pins  248  are fabricated from quartz or sapphire. In one example, the controller may be a general purpose computer that includes memory for storing software. The software may include instructions for detecting erosion of the second edge ring  244  and then directing the one or more actuators  247  to raise the one or more push pins  248  such that the second edge ring  244  is elevated to a desired height. 
       FIG. 3  is an enlarged schematic partial view of a substrate support assembly  311  according to another example. Similar to the substrate support assembly  111 , the substrate support assembly  311  includes a process kit  304 , a substrate support  306 , and an electrostatic chuck  303 . The electrostatic chuck  303  is disposed on a top surface of the substrate support  306 , and surrounded by the process kit  304 . The substrate support  306  includes the ground plate  226 , the insulating plate  227 , the facilities plate  228 , and a sleeve  305 . 
     The process kit  304  includes a first edge ring  342 , a second edge ring  344 , and a cover ring  346 . The first edge ring  342  is positioned adjacent to the radially outward edges of the substrate  109  to reduce undesired processing effects at the edge of the substrate  109 . The second edge ring  344  is positioned radially outward of and above the first edge ring  342 . The second edge ring  344  may be positioned radially inward of and above the cover ring  346 . In a lowermost position, the second edge ring  344  may have a lower surface  302  in contact with one or more of the first edge ring  342 , the sleeve  230 , and the cover ring  346 . In the lowermost position, the second edge ring  344  may share a coplanar upper surface with the cover ring  346 . The substrate support assembly  311  may be similar to the substrate support assembly  111 ; however, the one or more push pins  248  are positioned to contact the second edge ring  344 . The second edge ring  344  may be fabricated from the same material as the second edge ring  244 . The one or push pins  248  actuate the second edge ring  344  directly, rather than indirectly via actuation of the cover ring  346 . In such an example, the cover ring  346  remains stationary during height adjustment of the second edge ring  344 . The substrate support assembly  311  may be used in place of the substrate support assembly  111 . 
     The substrate support assembly  311  includes a height-adjustable edge ring assembly  349  including one or more actuators  247 , one or more push pins  248 , and the second edge ring  344 . The edge ring assembly  349  may be similar to the edge ring assembly  249 ; however, the one or more push pins  248  of the edge ring assembly  349  are positioned through the vertical walls of the ground plate  226  and through the cover ring  346 . Thus, the push pins  248  of the edge ring assembly  349  do not travel through the insulating plate  227  and the sleeve  230 , eliminating the bores formed through the insulating plate  227  and the sleeve  230 . Moreover, because the edge ring assembly  349  actuates the second edge ring  344  and allows the cover ring  346  to remain stationary, the substrate support assembly  311  may reduce particle generation due to a reduced number of moving parts. The first edge ring  342  may be fabricated from the same material as the first edge ring  242 . 
       FIG. 4  is an enlarged schematic partial view of a substrate support assembly  411  according to another example. The substrate support assembly  411  may be similar to the substrate support assembly  311  and may be used in place thereof. The substrate support assembly  411  includes a process kit  414 , a substrate support  416 , and the electrostatic chuck  303 . The electrostatic chuck  303  is disposed on a top surface of the substrate support  416  and surrounded by the process kit  414 . The substrate support  416  includes the ground plate  226 , the insulating plate  227 , the facilities plate  228 , and a sleeve  418 . The process kit  414  includes a first edge ring  442 , a second edge ring  444 , and a cover ring  446 . The first edge ring  442  is positioned on a radially outward upper surface  402  of the electrostatic chuck  303 . The second edge ring  444  is positioned radially outward and upward of the first edge ring  442 . A lower surface  404  of the second edge ring  444  may be positioned in contact with a surface  406  of the first edge ring  442  and an upper surface  408  of a first portion of the sleeve  418 . The cover ring  446  is positioned radially outward of the second edge ring  444  and in contact with an upper surface  410  of a second portion of the sleeve  418  as well as an upper surface  412  of a vertical portion of the ground plate  226 . 
     The substrate support assembly  411  includes a height-adjustable edge ring assembly  449 . The edge ring assembly  449  includes one or more actuators  247 , one or more push pins  248 , and the second edge ring  444 . The one or more actuators  247  actuate the one or more push pins  248  to elevate the second edge ring  444  relative to an upper surface of the substrate  109 , as well relative to the first edge ring  442  and the cover ring  446 . Similar to the substrate support assembly  311 , the cover ring  446  remains stationary while the second edge ring  444  is elevated. Due to a reduced number of movable components, there is a reduced likelihood of particle generation during processing. However, unlike the substrate support assembly  311 , the push pins  248  of the substrate support assembly  411  are disposed through the insulating plate  227  and the sleeve  418 . The one or more push pins  248  contact a lower surface  404  of the second edge ring  444  to transfer movement from the actuator  247  to the second edge ring  444 . In one example, the first edge ring  442  may be fabricated from silicon. In one example, the second edge ring  444  may be fabricated from silicon. In a particular example, the second edge ring  444  may be fabricated from silicon carbide (SiC). 
       FIG. 5  is a flow chart of a method  550  according to examples described herein.  FIGS. 6A-6C  depict plasma uniformity across substrate surfaces at a portion of a substrate support assembly  660  at various stages of the method  550  described herein.  FIG. 5  and  FIGS. 6A-6C  will be discussed in conjunction to further describe the processes for adjusting the height of an height-adjustable edge ring, such as the second edge rings  244 ,  344 ,  444  to compensate for erosion of that ring. The method may be stored on and executed by a controller, such as the controller  155 . 
     The method  550  begins at operation  552 . In operation  552 , a first number of substrates of substrate are processed. While processing the first number of substrates, a top surface  602  of an edge ring  644  is coplanar with a top surface  604  of the substrate  109 , as shown in  FIG. 6A . The edge ring  644  may be the second edge ring  244 ,  344 ,  444 . When the top surface  602  of the edge ring  644  and the top surface  604  of the substrate  109  are coplanar, plasma is uniformly distributed over the substrate  109  such that the plasma sheath  662  runs parallel to the top surface  604  of the substrate  109 . 
     After processing the first number of substrates, the edge ring  644  may be eroded as shown in  FIG. 6B . As the edge ring  644  is eroded, the total thickness of the edge ring  644  is decreased and the top surface  602  of the edge ring  644  is no longer coplanar with the top surface  604  of the substrate  109 . Instead, the top surface  602  of the edge ring  644  is below the top surface  604  of the substrate  109 . When the top surface  602  of the edge ring  644  is not coplanar with the top surface  604  of the substrate  109 , plasma becomes non-uniformly distributed across the top surface  604  of substrate  109 . More specifically, when the top surface  602  of the edge ring  644  is below the top surface  604  of the substrate  109 , there is plasma “roll off” at an edge  606  of the substrate  109  as shown by the plasma sheath  662 . In other words, the plasma sheath  662  is no longer parallel to the top surface  604  of the substrate  109 . This plasma non-uniformity at the substrate edge  606  causes non-uniform process conditions, which decreases process yield of the substrate  109  upon which devices may be formed. 
     Accordingly, in operation  554 , the edge ring  644  is elevated from a first position above an edge ring  642  to a second position above the edge ring  642  based on a first amount of erosion of the edge ring  644 . The edge ring  642  may be the first edge ring  242 ,  342 ,  442 . The edge ring  644  may be the second edge ring  244 ,  344 ,  444 . The edge ring  644  is elevated to maintain a linear plasma sheath  662  (i.e., maintain the plasma sheath  662  to be parallel to the top surface  604  of the substrate  109 ), as shown in  FIG. 6C . In one example, the edge ring  644  may be elevated to a position such that the top surface  602  of the edge ring  644  in an eroded state is substantially coplanar with the top surface  604  of the substrate  109 . The height to which the edge ring  644  may be adjusted may be determined using a controller, such as the controller  155  shown in  FIG. 1 . The controller may be used for detecting the first amount of erosion of the edge ring  644 . The controller may then direct one or more actuators  247  to elevate the height of the edge ring  644  via one or more push pins to compensate for the first amount of erosion. The distance between the first position and the second position may be about 0.05 millimeters to about 5 millimeters. 
     Alternatively, instead of detecting the amount of erosion on the edge ring  644 , the edge ring  644  may be adjusted after an empirically-determined number of substrates are processed. Alternatively, the edge ring  644  may be adjusted in response to a measurement of plasma sheath deformation. 
     In operation  556 , a second number of substrates are processed while maintaining the edge ring  644  in the adjusted position. While in the adjusted position, the edge ring  644  positions the plasma sheath  662  in a coplanar orientation with the top surface  604  of the substrate  109 . After processing a second number of substrates, the method  550  may further include detecting a second amount of erosion of the edge ring  644  and elevating the edge ring  644  from the second position to a third position. The distance between the second position and the third position may be about 0.05 millimeters to about 5 millimeters. The operations of method  550  may be repeated as more substrates are processed and further erosion of the edge ring  644  occurs. 
       FIG. 7  is a schematic cross-sectional side view of a substrate support assembly  700  according to another example of the disclosure. The substrate support assembly  700  may be the substrate support assembly  111  shown in  FIG. 1 . The substrate support assembly  700  includes a process kit  703 , a substrate support  705 , an electrostatic chuck  712 , a cathode liner  726 , and a shield  728 . The electrostatic chuck  712  is disposed on a top surface of the substrate support  705  and surrounded by the process kit  703 . The substrate support  705  may include a base  702 , a ground plate  704  disposed on the base  702 , an insulating plate  706  disposed on the ground plate  704 , a facilities plate  708  disposed on the insulating plate  706 , a cooling plate  710  disposed on the facilities plate  708 , and a sleeve  724  disposed on the insulating plate  706  surrounding the facilities plate  708 , the cooling plate  710 , and the electrostatic chuck  712 . The sleeve  724  may be fabricated from quartz. The electrostatic chuck  712  may be bonded to the cooling plate  710  with a bonding material. A plurality of electrodes  714  may be embedded in the electrostatic chuck  712 . The electrostatic chuck  712  may include a first portion  716  having a first surface  718  for supporting a substrate and a second portion  720  extending radially-outward from the first portion  716 . The second portion  720  may include a second surface  722 . 
     The process kit  703  includes a support ring  730 , an edge ring  732 , and a cover ring  734 . The support ring  730  is disposed on the second surface  722  of the second portion  720  of the electrostatic chuck  712 , and the support ring  730  surrounds the first portion  716  of the electrostatic chuck  712 . The support ring  730  may be fabricated from silicon or SiC. The support ring  730  may be positioned concentrically with respect to the first portion  716  of the electrostatic chuck  712 . The support ring  730  may have an inner radius that is less than 100 microns greater than a radius of the first portion  716  of the electrostatic chuck  712 . The edge ring  732  may be disposed on the support ring  730 , and the edge ring  732  may be made of silicon, SiC, or other suitable material. The edge ring  732  may be positioned concentrically with respect to the first portion  716  of the electrostatic chuck  712 . The cover ring  734  may be disposed on the sleeve  724  and the cover ring  734  may surround the edge ring  732  and the support ring  730 . 
     The substrate support assembly  700  further includes one or more actuators  736  (one is shown), such as a stepper motor, one or more pin holders  737  (one is shown), one or more bellows  735  (one is shown), and one or more push pins  733  (one is shown). The push pins  733  may be fabricated from quartz, sapphire, or other suitable material. Each pin holder  737  is coupled to a corresponding actuator  736 , each bellows  735  surrounds a corresponding pin holder  737 , and each push pin  733  is supported by a corresponding pin holder  737 . Each push pin  733  is positioned through an opening formed in each of the ground plate  704 , the insulating plate  706 , and the sleeve  724 . One or more push pin guides, such as the push pin guides  239  shown in  FIG. 2B , may be positioned around the openings in the ground plate  704 , the insulating plate  706 , and/or the sleeve  724 . The one or more actuators  736  can raise the one or more pin holders  737  and the one or more push pins  733 , which in turn raise or tilt the edge ring  732 . 
       FIGS. 8A-8B  are schematic cross-sectional partial side views of the substrate support assembly  700  according to examples of the disclosure. As shown in  FIG. 8A , the push pin  733  is positioned through an opening  812  of the sleeve  724 , and is in contact with the edge ring  732  through an opening  806  formed in the support ring  730 . The edge ring  732  has a first surface  814  and a second surface  816  opposite the first surface  814 . One or more cavities  808  (one is shown) may be formed in the second surface  816  of the edge ring  732 . The support ring  730  may include a first surface  813  for supporting the edge ring  732  and a second surface  815  opposite the first surface  813 . The second surface  815  may be in contact with the second surface  722  of the second portion  720  of the electrostatic chuck  712 . Each push pin  733  may include a chamfered tip  810  positioned in a corresponding cavity  808  of the edge ring  732 , and the chamfered tip  810  can constrain the movement of the edge ring  732  in a horizontal, or radial, direction. In addition, the movement in the horizontal, or radial, direction of the support ring  730  is constrained by the push pins  733  since the radial clearance of each push pin  733  inside the opening  806  is very small, such as between 0.0001 in and 0.0010 in, for example about 0.0005 in. The radial clearance of each push pin  733  inside the opening  812  of the sleeve  724  may be similar to the radial clearance of the push pin  733  inside the opening  806 . To further constrain the movement of the edge ring  732  in the horizontal, or radial, direction, the support ring  730  may include an inner edge  804  adjacent to the first portion  716  of the electrostatic chuck  712 . The inner edge  804  may have a greater thickness than the rest of the support ring  730 . In other words, the inner edge  804  includes a surface  818  at a higher elevation than the first surface  813  of the support ring  730 . The edge ring  732  may be positioned on the first surface  813  of the support ring  730 , and an inner surface  820  of the edge ring  732  may be in contact with the inner edge  804  of the support ring  730 . Thus, the edge ring  732  is prevented from shifting in the horizontal, or radial, direction relative to the support ring  730 . 
     After processing a certain number of substrates inside of the process chamber  100 , the edge ring  732  may erode, and the first surface  814  is not coplanar with a processing surface of a substrate, such as the substrate  802 , disposed on the first portion  716  of the electrostatic chuck  712 . The edge ring  732  may be lifted by the one or more push pins  733 , such as three push pins  733 , in order for the first surface  814  of the edge ring  732  to be coplanar with the processing surface of the substrate  802  disposed on the first portion  716  of the electrostatic chuck  712 . Thus, the edge ring  732  may be supported by the one or more push pins  733  during processing. Since the radial clearance of each push pin  733  inside of the openings  806 ,  812  is small, the movement of the edge ring  732  in the horizontal, or radial, direction is constrained as the edge ring  732  is supported by the one or more push pins  733 . Because the movement of the edge ring  732  in the horizontal, or radial, direction is constrained, the edge ring  732  is consistently positioned concentrically with respect to the first portion  716  of the electrostatic chuck  712 . Since the substrate  802  is positioned concentrically with respect to the first portion  716  of the electrostatic chuck  712 , the edge ring  732  is also consistently positioned concentrically with respect to the substrate  802  when the edge ring  732  is supported either by the support ring  730  or by the one or more push pins  733 . Having the edge ring  732  consistently positioned concentrically with respect to the substrate  802  and the first surface  814  of the edge ring  732  being coplanar with the processing surface of the substrate  802  improves plasma uniformity across the processing surface of the substrate during processing. 
     Sometimes the substrate may suffer from an azimuthal non-uniformity near the edge of the substrate. In order to adjust the azimuthal edge process results, the edge ring  732  may be tilted by the one or more actuators  736  via the one or more push pins  733 . The one or more actuators  736  may raise the one or more push pins  733  to different elevations, and the edge ring  732  is tilted with respect to the processing surface of the substrate  802 . By titling the edge ring  732 , i.e., causing the edge ring  732  to be non-coplanar with the processing surface of the substrate  802 , the plasma sheath and/or chemistry in a specific location near the substrate edge is changed, and the azimuthal non-uniformity near the substrate edge is reduced. 
     In order to lift the edge ring  732  while the edge ring  732  is coplanar with the processing surface of the substrate  802 , the one or more actuators  736  may be calibrated so the one or more push pins  733  are raised by the actuators  736  to the same elevation. One method of calibrating the actuators  736  is to slowly raise each push pin  733  until the person calibrating the actuators  736  feels each push pin  733  is slightly above the first surface  718  of the first portion  716  of the electrostatic chuck  712 . Another method of calibrating the actuators  736  is to use an acoustic sensor to hear the contact of the push pins  733  against the edge ring  732 , to use an accelerometer on the edge ring  732  to sense the contact, or to look at the servo position feedback (following error or servo torque) to sense the contact. 
     Another benefit of being able to raise the edge ring  732  is that the edge ring  732  can be raised to a high enough elevation such that a vacuum robot blade (not shown) can enter the process chamber via a slit valve beneath the edge ring  732  and remove the edge ring  732  from the process chamber without venting and opening the process chamber. The edge ring  732  may be removed from the process chamber by the vacuum robot after a number of substrates have been removed from the process chamber. A new edge ring  732  may be placed in the process chamber by the vacuum robot. The new edge ring  732  may be made of a different material or may have a different shape, in order to optimize results of a specific process. In addition, the ability to transfer edge ring  732  in and out of the process chamber without venting and opening the process chamber enables the process chamber to run longer between wet clean cycles which are expensive and cause lost productivity. 
     An exemplary process sequence for removing the edge ring  732  starts with lifting the edge ring  732  to an elevation above a substrate transfer plane by the one or more push pins  733 , extending the vacuum robot blade into the process chamber at a location below the edge ring  732 , lowering the edge ring  732  onto the vacuum robot blade by the one or more push pins  733 , moving the vacuum robot blade with the edge ring  732  disposed thereon out of the process chamber and into a loadlock chamber (not shown), picking the edge ring  732  off of the vacuum robot blade by raising the loadlock chamber lift (not shown) or lowering the vacuum robot blade, venting the loadlock chamber, using a factory interface robot (not shown) to remove the edge ring  732  from the loadlock chamber, and putting the edge ring  732  in a storage location (the storage location could have multiple locations holding different or similar edge rings). 
       FIG. 8B  is a schematic cross-sectional partial side view of a substrate support assembly  800  according to another example of the disclosure. As shown in  FIG. 8B , the substrate support assembly  800  includes a process kit  801 , the substrate support  705 , and an electrostatic chuck  803 . The process kit  801  may surround the electrostatic chuck  803 . The electrostatic chuck  803  may include a first portion  805 , a second portion  807  extending radially-outward from the first portion  805 , and a third portion  830  extending radially-outward from the second portion  807 . The second portion  807  has a surface  809 , and the third portion  830  has a surface  832 . The process kit  801  includes a cover ring  840 , a support ring  850 , and an edge ring  852 . The sleeve  724  may include one or more cavities  844 , and the cover ring  840  may include one or more protrusions  842 . The support ring  850  may be disposed on the surface  832  of the third portion  830  of the electrostatic chuck  803 , and a gap  811  may be formed between the support ring  850  and the sleeve  724 . The support ring  850  may be disposed over a surface  843  of the sleeve  724 . The support ring  850  may be fabricated from the same material as the support ring  730 . One or more openings  860  may be formed in the support ring  850 , and the one or more push pins  733  may be disposed through the openings  860 . The edge ring  852  may be disposed on the second surface  809  of the second portion  807  of the electrostatic chuck  803 . The edge ring  852  may be adjustable independently from the support ring  850 . The edge ring  852  may be fabricated from the same material as the edge ring  732 . The edge ring  852  may include one or more cavities  854  for engaging the chamfered tips  810  of the one or more push pins  733 . The chamfered tips  810  can constrain the movement of the edge ring  852  in a horizontal, or radial, direction. 
     The support ring  850  may be tightly fitted between the second portion  807  of the electrostatic chuck  803  and the one or more protrusions  842  of the cover ring  840 . The cover ring  840  may include a top surface  862 , a first surface  864  opposite the top surface  862 , a second surface  866  opposite the top surface  862 , a third surface  868  opposite the top surface  862 , and a fourth surface  870  opposite the top surface  862 . The first surface  864  may be in contact with and supported by the support ring  850 , while a gap is formed between surfaces  866 ,  868  and the sleeve  724  and between the surface  870  and the shield  728 . The cover ring  840  may further include a fifth surface  872  connecting surfaces  866 ,  868  and a sixth surface  874  connecting surfaces  864 ,  866 . Each cavity  844  of the one or more cavities of the sleeve  724  may include a first surface  876  and a second surface  878  opposite the first surface  876 . Gaps formed between the first surface  876  and the fifth surface  872  and between the second surface  878  and the sixth surface  874  may be small, such as 0.01 in or less, which constrains the movement of the cover ring  840  in the horizontal, or radial, direction. Since the support ring  850  is tightly fitted between the sixth surface  874  of the cover ring  840  and the second portion  807  of the electrostatic chuck  803 , the movement of the support ring  850  in the horizontal, or radial, direction is also constrained. The edge ring  852  may be consistently positioned concentrically with respect to the substrate (not shown) when the edge ring  852  is either supported by the second surface  809  of the electrostatic chuck  803  or by the one or more push pins  733 . The edge ring  852  may be removed from the process chamber by the same method as removing the edge ring  732 . 
       FIG. 9  is a schematic top view of the substrate support assembly  700  of  FIG. 7  according to one example of the disclosure. As shown in  FIG. 9 , the substrate support assembly  700  includes the electrostatic chuck  712  having the first portion  716  with the surface  718 , which is surrounded by the edge ring  732  (or  852 ), which is surrounded by the cover ring  734  (or  840 ). The shield  728  surrounds the sleeve  724  ( FIGS. 8A and 8B ). The edge ring  732  (or  852 ) may be raised by the one or more push pins  733  ( FIGS. 8A-8B ) at locations  902 . In one example, there are three push pins  733  for raising the edge ring  732  (or  852 ) at three locations  902 . The locations  902 , or the push pins  733 , may be 120 degrees apart and may have the same radial distance on the edge ring  732  (or  852 ), as shown in  FIG. 9 . The edge ring  732  (or  852 ) may have an outer edge  904  and an inner edge  906 . The inner edge  906  may include a first portion  907  and second portion  908 . The outer edge  904  may be substantially circular. The first portion  907  of the inner edge  906  may be substantially circular and may be substantially parallel to the outer edge  904 . The second portion  908  of the inner edge  906  may be substantially linear and may not be substantially parallel to the outer edge  904 . The second portion  908  may conform to a linear section  910  on the electrostatic chuck  712  for locking with the electrostatic chuck  712 . 
       FIG. 10A  is a schematic top view of the edge ring  732  (or  852 ) according to one example of the disclosure. As shown in  FIG. 10A , the edge ring  732  (or  852 ) includes the outer edge  904 , the inner edge  906 , and the second portion  908 . The distance between the outer edge  904  and the inner edge  906  (i.e., the width) may vary in order to optimize different processes or process chemistries. The radius of the edge ring  732  (or  852 ) may also vary depending on the radius of the electrostatic chuck. 
       FIG. 10B  is a schematic side view of a portion of the edge ring  732  (or  852 ) of  FIG. 10A  according to one example of the disclosure. As shown in  FIG. 10B , the edge ring  732  (or  852 ) includes one or more cavities  808  (or  854 ) for engaging with the chamfered tip  810  of the one or more push pins  733 . The cavities  808  (or  854 ) may have any suitable shape. In one example, each cavity  808  (or  854 ) has a tapered V shape, as shown in  FIG. 10B . 
       FIG. 11A  is a schematic top view of the support ring  850  according to one example of the disclosure. As shown in  FIG. 11A , the support ring  850  (or  730  shown in  FIG. 8A ) includes an outer edge  1102 , an inner edge  1104 , and the one or more openings  860  (or  806  shown in  FIG. 8A ). In one example, there are three openings  860 , as shown in  FIG. 11A , and the openings  860  are formed at locations between the outer edge  1102  and the inner edge  1104 . The distance between the outer edge  1102  and the inner edge  1104  (i.e., the width) may vary in order to optimize different processes or process chemistries. The radius of the support ring  850  may also vary depending on the radius of the electrostatic chuck. 
       FIG. 11B  is an enlarged schematic top view of a portion of the support ring  850  of  FIG. 11A  according to one example of the disclosure. As shown in  FIG. 11B , the inner edge  1104  may optionally include one or more protrusions  1106 . The one or more protrusions  1106  may be located adjacent to the one or more openings  860 . The one or more protrusions  1106  are used to maintain concentricity with respect to the electrostatic chuck  712  in the event both the electrostatic chuck  712  and the support ring  850  are thermally expanded during processing. 
       FIG. 12  is a schematic cross-sectional partial side view of the substrate support assembly  700  according to another example of the disclosure. As shown in  FIG. 12 , the one or more push pins  733  may be located through an opening  1202  formed in the cathode liner  726  and through an opening  1204  formed in the shield  728 . The cover ring  734  may include one or more cavities  1206  for engaging the chamfered tip  810  of the one or more push pins  733 . The one or more push pins  733  can raise or tilt the cover ring  734  in the same fashion as raising the edge ring  732  or  852 . In one example, one or more push pins  733  are utilized to raise or tilt both the cover ring  734  and the edge ring  732  or  852  to improve plasma uniformity across the processing surface of the substrate. 
     Examples of the present disclosure result in increased plasma uniformity across the surface of a substrate being processed in a process chamber. Since there is a direct correlation between plasma uniformity and process yield, the increased plasma uniformity leads to an increase in process yield. Furthermore, process chambers making use of the present disclosure experience less downtime for preventative maintenance by extending the usable life of edge rings. 
     While the foregoing is directed to examples of the present disclosure, other and further examples of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.