Abstract:
Method and apparatus for supporting and transferring a substrate in a semiconductor wafer processing system are provided. In one aspect, an apparatus is provided for supporting a substrate comprising a cover ring comprising a base having a bore disposed therethough, the base having an upper surface and one or more raised surfaces disposed adjacent the bore, wherein the raised surface comprise one or more first substrate support members disposed adjacent an edge of the bore and a capture ring disposed on the cover ring, the capture ring comprising a semi-circular annular ring having an inner perimeter corresponding to the bore of the cover ring and one or more second substrate support members disposed on the inner perimeter and adapted to receive a substrate, wherein the capture ring is adapted to mate with the cover ring and form one contiguous raised surface on the cover ring.

Description:
[0001]     This application is a continuation of U.S. patent application Ser. No. 10/689,783, filed Oct., 21, 2003 (APPM/8348), which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Embodiments of the present invention generally relate to a method and apparatus for supporting and transferring substrates during photomask fabrication.  
         [0004]     2. Description of the Related Art  
         [0005]     Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore&#39;s Law), which states that the number of devices on a chip doubles every two years. Today&#39;s fabrication plants are routinely producing devices having 0.35 μm and even 0.18 μm feature sizes, and tomorrow&#39;s plants soon will be producing devices having even smaller geometries.  
         [0006]     Increasing circuit densities have placed additional demands on processes used to fabricate semi-conductor devices. For example, as circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions. However, the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Reliable formation of high aspect ratio features is important to the success of sub-micron technology and to the continued effort to increase circuit density and quality of individual substrates and die.  
         [0007]     High aspect ratio features are conventionally formed by patterning a surface of a substrate to define the dimensions of the features and then etching the substrate to remove material and define the features. To form high aspect ratio features with a desired ratio of height to width, the dimensions of the features are required to be formed with certain parameters, which is typically defined as the critical dimensions of the features. Reliable formation of high aspect ratio features with desired critical dimensions requires precise patterning and subsequent etching of the substrate.  
         [0008]     A technique commonly used to form precise patterns on substrates is photolithography. In conventional photolithographic processes, a photoresist material is applied on a substrate layer to be etched. A light source emitting ultraviolet (UV) light is typically used to expose the photoresist layer to chemically alter the composition of the photoresist. However, the photoresist layer is only selectively exposed. In this respect, a photomask, or “reticle,” is positioned between the light source and the substrate being processed. The photomask contains the desired configuration of features for the substrate. The exposed, or alternatively, the unexposed photoresist material is then removed to expose the underlying material of the substrate. The retained photoresist material remains as an etch resistant pattern on the substrate. The exposed underlying material may then be etched to form the desired features in the substrate, i.e., contacts, vias, or other features.  
         [0009]     Photolithographic photomasks, or reticles, typically comprise a substrate of an optically transparent silicon based material, such as quartz. A light-shielding layer of metal, typically chromium, is patterned on the surface of the substrate. The metal layer is patterned and etched to form features which define the pattern, and correspond to the dimensions of the features to be transferred to a substrate, such as a semiconductor wafer.  
         [0010]     The deposition and etching processes employed to fabricate the photomask requires that the substrate be transferred and supported within a processing system. It has become desirable to utilize processing equipment and systems which are configured for processing the substrates themselves when fabricating the photomasks. However, these systems are typically configured to process circular substrates, and must be reconfigured to support and transfer rectangular photomasks. In addition, the systems used to support and transport the substrates used in photomask fabrication must carefully handle the substrates to prevent scratches and other defects from being formed on the substrates. These defects can alter the light transmission properties of the substrates and result in defective photomasks.  
         [0011]     Therefore, there is a need for a method and apparatus for transferring and supporting substrates in processing systems which minimizes defect formation.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention generally provides a substrate support member to minimize defect formation in a substrate during processing and handling of substrates in a plasma etch chamber. In one aspect, an apparatus is provided for supporting a substrate on a pedestal or cathode in a processing chamber to minimize contact between the substrate and the chamber components during processing.  
         [0013]     In one aspect, an apparatus is provided for supporting a substrate comprising a cover ring comprising a base having a bore disposed therethough, the base having an upper surface and one or more raised surfaces disposed adjacent the bore, wherein the raised surface comprise one or more first substrate support members disposed adjacent an edge of the bore and a capture ring disposed on the cover ring, the capture ring comprising a semi-circular annular ring having an inner perimeter corresponding to the bore of the cover ring and one or more second substrate support members disposed on the inner perimeter and adapted to receive a substrate, wherein the capture ring is adapted to mate with the cover ring and form one contiguous raised surface on the cover ring.  
         [0014]     The apparatus for supporting a substrate may be used in a processing chamber comprising an enclosure defining a process region, which processing chamber may also be used in a substrate processing system comprising a transfer chamber, at least the one processing chamber, and a substrate handler disposed in the transfer chamber. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated 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.  
         [0016]      FIG. 1  is a schematic view of one embodiment of an etching chamber containing a substrate support member;  
         [0017]      FIG. 2  is an exploded perspective view of the substrate support member of  FIG. 1 ;  
         [0018]      FIG. 3  is a top plan view of one embodiment of a cover ring;  
         [0019]      FIG. 4  is a cross-sectional view of the cover ring of  FIG. 3 ;  
         [0020]      FIG. 5  is a schematic top view of one embodiment of a capture ring  
         [0021]      FIG. 6  is a schematic bottom view of the capture ring of  FIG. 5 ;  
         [0022]      FIG. 7  is a schematic cross-sectional view of one embodiment of a substrate support;  
         [0023]      FIG. 8  is a cross-sectional view of the a substrate in a processing position in relation to the substrate supports;  
         [0024]      FIG. 9  is a perspective view of the substrate handler of the invention in relation to the capture ring of the invention;  
         [0025]      FIG. 10  is a perspective view of  FIG. 9 ;  
         [0026]      FIG. 11  is a perspective view of the substrate handler of the invention in relation to the capture ring of the invention;  
         [0027]      FIG. 12  is perspective view of a substrate in the capture ring of the invention;  
         [0028]      FIG. 13  is perspective view of a substrate in the capture ring of the invention;  
         [0029]      FIG. 14  is a top schematic view of a radial cluster tool for batch processing of semiconductor substrates. 
     
    
     DETAILED DESCRIPTION  
       [0030]     Aspects of the invention will be described below in reference to an inductively coupled plasma etch chamber. Suitable inductively coupled plasma etch chambers include the ETEC Tetra™ photomask etch chambers, such as the ETEC Tetra I™ photomask etch chamber and the ETEC Tetra II™ photomask etch chamber, available from ETEC of Hayward, Calif., or optionally, a Decoupled Plasma Source DPS™ processing chambers, such as the DPS I™, DPS II™, and DPS+™ processing chambers available from Applied Materials, Inc., of Santa Clara, Calif.  
         [0031]     Other process chambers may be used including, for example, capacitively coupled parallel plate chambers and magnetically enhanced ion etch chambers, as well as inductively coupled plasma etch chambers of different designs. Examples of such suitable processing chambers are disclosed in U.S. patent application Ser. No. 09/325,026, filed on Jun. 3, 1999, which is incorporated by reference to the extent not inconsistent with the claims and disclosures described herein. Although the processes are advantageously performed with the DPS™ processing chamber, the description in conjunction with the DPS™ processing chamber is illustrative and should not be construed or interpreted to limit the scope of aspects of the invention.  
         [0032]      FIG. 1  is a schematic cross sectional view of one embodiment of a process chamber  160  having a substrate support member disposed therein and a substrate handler blade  300  positioned adjacent thereto. The process chamber  160  generally includes a cylindrical side wall or chamber body  162 , an energy transparent dome ceiling  163  and a chamber bottom  167 . An inductive coil  176  is disposed around at least a portion of the dome  163 . The chamber body  162  and chamber bottom  167  of the chamber  160  can be made from a metal, such as anodized aluminum, and the dome  163  can be made of an energy transparent material such as a ceramic or other dielectric material. A substrate support member  100 , such as a cathode assembly, is disposed in the chamber  160  to support a substrate  222  during processing. A plasma zone  164  is defined by the process chamber  160  above an upper surface of the substrate support member  100 . A top housing (not shown) generally encloses the process chamber  160 .  
         [0033]     Process gases are introduced into the plasma etch chamber  160  through a gas distributor  172  peripherally disposed about the substrate support member  100 . The gas distributor is shown illustratively, and may be disposed in other configurations, such as disposed at the top of dome  163 . Process gases and etchant byproducts are exhausted from the process chamber  160  through an exhaust system  180 . A throttle valve  182  is provided in an exhaust port  184  for controlling the pressure in the plasma etch chamber  160 . An endpoint measurement device may be included to determine the endpoint of a process performed in the chamber.  
         [0034]     The substrate support member  100  has a substrate support assembly  115  disposed thereon. The substrate support assembly  115  includes a capture ring  120  having one or more substrate support members disposed thereon or otherwise connected thereto disposed on a cover ring  116  having one or more substrate support members to receive and support a substrate for processing in the chamber  160 . The substrate support member  100  will be defined in more detail below, and the cooperation of the substrate support member  100  with a substrate handler blade will be described and illustrated below.  
         [0035]     A cathode  112  (not shown in  FIG. 1 ) is disposed in the base  106  of the substrate support member  100  and is electrically coupled to an electrode power supply  178  to generate a capacitive electric field in the plasma etch chamber  160 . Typically an RF voltage is applied to the cathode  112  of the substrate support member  100  while the chamber body  162  is electrically grounded. The capacitive electric field forms a bias which accelerates inductively formed plasma species toward the substrate  222  to provide a more vertically oriented anisotropic etching of the substrate  222 .  
         [0036]      FIG. 2  is an exploded perspective view of one embodiment of a substrate support member  100 . The substrate support member  100  includes a body  106 , a substrate supporting assembly  115  including a cover ring  116  and a capture ring  120 . The body  106  is mounted on a bulk head assembly, or shaft,  102 . In the embodiment shown, the body  106  is stationary in the chamber, however, in an alternative embodiment, the body  106  or a portion of the body  106  may be moveable within the chamber. The cathode  112  disposed in the base  106  may vertically extend above the surface of the body  106 . Channels  111  (three are shown) are also disposed through the body  106  and house internally movable lift pins  114  therein. The lift pins  114  engage the lower surface of the capture ring  120  to move the capture ring vertically within the chamber relative to the cover ring  116 . The body  106  may comprise a temperature controlled base adapted to regulate the temperature of the substrate support assembly  115 , and thus, a substrate  222  disposed thereon. The body  106  can be made of a material inert to the process formed in the processing chamber including, for example, aluminum oxide, or aluminum, and substrate support assembly  115  components can be made of aluminum or aluminum oxide. The body  106  may include fluid channels, heating elements, e.g., resistive heating elements or other temperature control members.  
         [0037]     The body  106  of the substrate support member  100  is mounted on a stainless steel base  104 , typically disposed on the bottom of a processing chamber (not shown); with the bulk head assembly  102  mounted through the bottom of the processing chamber and coupled to the body  106 . The substrate support member  100  is adapted to maintain vacuum isolation between the interior of the chamber and the outside environment. Power, electrical controls, and backpressure gases are provided to the substrate support member  100  via the shaft  102 .  
         [0038]     Referring to  FIG. 3 , a top view of one embodiment of a cover ring  116 , and  FIG. 4 , a cross-sectional view of  FIG. 3 , the cover ring  116  includes a base circular ring with an upper surface  119  and raised surfaces  121 , 122  disposed thereon. A central opening or bore  125  is defined in the upper surface  119  of the cover ring  116 . The upper surface  119  and the raised surfaces  121 , 122  may be monolithic or may be made of separate components connected together. The raised surfaces  121 ,  122  include a linear raised surface  122  extending along the length of one side of the bore  125  and an arcuate raised surface  121  with an outer diameter  124  co-existing with the radius of the ring and an inner perimeter  126  conforming to the shape of the bore on one or more sides of the bore. Substrate supports  118  are disposed on the raised surfaces  121 ,  122  of the cover ring  116  and around the perimeter of the bore  125  of the capture ring  120  and form a continuous substrate supporting surface when the capture ring  120  and cover ring  116  are integrated. The substrate supports  118  include substrate receiving surfaces defined by an inner sloped surface of each substrate support  118 .  
         [0039]     Channels  117  are formed through the cover ring  116  to enable the lift pins  114  disposed through the body  106  to move therethough and lift the capture ring  120  vertically. The vertical movement imparted by the lift pins  114  is used to lift the capture ring  120  to effectuate substrate transfer between a substrate handler blade  300  and the capture ring  120 . The actuation of the assembly  115  will be described in more detail below.  
         [0040]     The capture ring  120  includes an arcuate base plate  202  having an inner perimeter  207  defining a bore  206  therein. A plurality of substrate supports, such as substrate supports  204 ,  205 , are disposed on the inner perimeter  207 . The substrate supports  204 ,  205  and the base plate  202  define a substrate receiving area. The substrate supports  204 ,  205  and the base plate  202  are adapted to mate with the substrate supports  118  on the cover ring mate when contacting the cover ring  116  and the capture ring  120  and define a planar substrate receiving surface for processing. The lift pins  114  move the capture ring  120  vertically above the cover ring  116  during substrate transfer and then lower the capture ring onto the cover ring  116  for processing. The whole assembly  115  may then be moved vertically within the chamber  160 .  
         [0041]      FIG. 5  is a top view of one embodiment of a capture ring  120 . The capture ring  120  includes a base  202  having an inner perimeter  207  and two substrate supports  204 ,  205  disposed therein. The base  202  is generally an arcuate ring with the central opening  206  defined therein. The base  202  is adapted for mounting on the cover ring  116 . The base  202  further includes a circumferential sealing lip  210  formed at the perimeter of the base  202  which forms a seal with the processing chamber (shown in  FIG. 1 ) when the substrate support member  100  is positioned in an upper processing position. A seal formed between the sealing lip  210  and the chamber prevents gases from flowing behind the substrate support member in contact with the lower portion of the chamber.  
         [0042]     The substrate support members  204 ,  205  of the inner perimeter  207  define an opening  220  through which a substrate handler blade can be moved to transfer a substrate (shown and described below in reference to  FIGS. 9-13 ) with minimal contact between components of the system.  
         [0043]      FIG. 6  is a bottom view of the capture ring  120  of  FIG. 5 . A plurality of lift pin recesses  224  are formed in the base  202  around the opening  206  and are adapted to receive the lift pins  114 . The lift pin recesses  224  are spaced around the perimeter of the capture ring  120  to provide stable support for the capture ring  120  when the capture ring  120  is lifted into a raised position. The lift pins  114  and lift pin recesses  224  can also be used to align the capture ring  120  on the cover ring  116 .  
         [0044]      FIG. 7  is a sectional view of the substrate support members  204 ,  205  of the capture ring  120  and substrate support members  118  of the cover ring  116 . The substrate support members  204  include an upper surface  212 , an outer surface  213  and an inner surface  215 . The inner surface  215  includes an upper substrate aligning surface  214  which is disposed at an incline from the upper surface  212 . The upper aligning surface  214  provides gravity assisted gross alignment of a substrate  222  received thereon. The upper aligning surface  214  may have an angle from the normal of between about 5° and about 30°, such as 15°. A generally vertical substrate capturing surface  217  is provided below the substrate aligning surface  214  and defines an outer boundary of a substrate receiving area. The lower portion  216  of the substrate support member  204  has an inclined surface disposed at an angle between about 2° and about 7°, preferably between about 2.5° and about 5°, for example, about 2.5°. The inclination of the substrate support members  204  minimizes the surface area contact between the substrate  222  and the substrate support members  204 ,  205 . The inclined surface and the lower portion  216  also assist in centering the substrate as it is received thereon.  
         [0045]     The capture ring  120  and cover ring  116  are generally formed from of an etch resistant, high temperature resistant material, such as aluminum or aluminum oxide, to enable the capture ring  120  and cover ring  116  to be used repetitively in the etching process without damage such as scratching or deformation. The capture ring  120  and cover ring  116  are preferably formed from single pieces of material to ensure a good fit with each other. However, the capture ring  120  and cover ring  116  may be made of multiple components, for example, the raised surfaces of the cover ring  116  may be made of a separate material and bound to the upper surface of the cover ring  116 .  
         [0046]      FIG. 8  is a cross sectional view of the substrate supports of the cover ring  116  and capture ring of the substrate  222  in a processing position. The substrate supporting ridge  225  of the cathode  112  defines a supporting surface on which the substrate is supported during processing. A space  170  is defined between the substrate supporting ridge  225  and a lower surface of a substrate  222  when the substrate  222  is received on the substrate supporting ridge  225 . A backside gas can be flowed into the space  170  during processing to facilitate thermal conduction and to prevent process gases from being introduced behind the substrate  222 . The backside gas can be delivered into the space  170 , for example, by the backside gas line  188  disposed in the pedestal  116  from a remotely located backside gas source  190  through gas portals (not shown) to the surface of the cathode  112 .  
         [0047]     To sufficiently transfer heat from the substrate  222  to the substrate support member  100  and prevent backside contamination, a substantial gas pressure may exist beneath the substrate  222 . A clamp ring (not shown) may be fitted to the periphery of the capture ring  120  to retain the substrate  222  on the substrate support member  100  when substantial backside gas pressure is applied between the substrate support member  100  and the substrate  222 . Such a clamp ring would be similar to that used to retain a substrate on a substrate support member  100  in a MXP™ chamber of a P5000™ platform, as manufactured by Applied Materials, Inc. of Santa Clara, Calif.  
         [0048]      FIGS. 9-14  illustrate transfer of a substrate  222  from the blade  300  to the capture ring  120 . The blade  300  retrieves a substrate  222  from a loadlock chamber  416  and delivers the substrate  222  into the processing chamber  412  (shown in  FIG. 14 ). One example of a suitable blade  300  for handling the substrate is more fully described in U.S. Pat. No. 6,537,011, issued on Mar. 25, 2003, which is incorporated by reference herein to the extent not inconsistent with the disclosure and claimed aspects herein. The substrate  222  disposed on the blade  300  is then horizontally aligned with the capture ring  120  in a vertically displaced position as described above and shown in  FIGS. 5, 9 , and  10 .  
         [0049]     The capture ring  120  may then be moved upwardly by lift pins  114  to contact and lift the substrate  222  off the blade  300  as shown in  FIG. 11 . The lower portion  216  of the substrate supports  204 ,  205  lift the substrate  222  from the blade  300 . The vertical displacement of the capture ring  120  is sufficient to allow to the blade  300  to withdraw from the processing chamber without contacting the top surface  202  of the capture ring  120  or the bottom surface of the substrate  222  as shown in  FIG. 12 . Once the blade is withdrawn, the capture ring  120  is lowered by the lift pins onto the upper surface  119  of the cover ring  116  for processing as shown in  FIG. 13 .  
         [0050]     For retrieving a processed substrate  222  from the capture ring  120 , the capture ring  120  is vertically displaced from the cover ring  116  to the substrate transfer position. The substrate handler blade  300  enters the processing chamber  160  and aligns the blade  300  between the substrate  222  and the top surface  202  of the capture ring  120  as illustrated by  FIG. 11 . When the blade  300  is aligned with the capture ring  120 , the blade  300  is disposed in a vertically displaced position below the inclined lower portions  216  of the substrate support members  204 ,  205 . The capture ring  120  is then lowered and the substrate handler blade  300  supports the substrate  222  thereon as illustrated by  FIG. 10 . The capture ring  120  is vertically displaced in a lowered position to allow the blade  300  to withdraw from the chamber  160  without contact with the capture ring  120  as shown in  FIG. 9 . In the lowered position, the capture ring  120  is ready to receive another substrate from the blade  300 . The substrate handler blade withdraws from the chamber  160  to return the processed substrate to another chamber, for example, a loadlock chamber  416  and then to retrieve another substrate  222  for placement in the processing chamber  160 .  
         [0051]     The supporting apparatus and substrate handler blade  300  described above may also be taken advantage of in a substrate processing system  410  providing support for a substrate. The substrate processing system  410  may include a transfer chamber  414 , at least one processing chamber  160  with a substrate support member  100  with a support surface and a capture ring coupled to the support surface, the capture ring adapted receive a substrate, and a substrate handler  418  disposed in the transfer chamber  414 . The substrate handler  418  preferably has a substrate handler blade  300  described above. The process chambers are preferably plasma etch chambers.  
         [0052]      FIG. 14  is a plan view of a vacuum cluster tool  410  suitable for use with the apparatus of the invention described above. The vacuum cluster tool includes multiple substrate processing chambers  412  mounted on a centralized vacuum chamber  414 , such as a transfer chamber, for transferring substrates from a substrate cassette located in one or more load lock chambers  416 , to one or more process chambers  412 . A cluster tool similar to that shown in  FIG. 14  is a Centura™ processing system available from Applied Materials, Inc. of Santa Clara, Calif.  
         [0053]     Transfer of the substrates between the process chambers  412  is typically managed by a substrate handling module, or substrate handler,  418 , preferably with the substrate handling blade  300  mounted thereon. The substrate handler  418  is located in the central transfer chamber  414 . After the substrates are processed, the substrates are retrieved from the processing chambers  412  and transferred to one or more of the load lock chamber  416  and into one or more substrate cassette (not shown) disposed within the one or more load lock chambers  416 . The substrates can then be retrieved from the loadlock chambers  416  and transferred to the next system for additional processing. In photomask manufacturing processing, the process chambers  412  are etching chambers, preferably plasma etching chambers.  
         [0054]     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, and the scope thereof is determined by the claims that follow.