Patent Publication Number: US-2005133158-A1

Title: Mask handler apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Embodiments of the present invention generally relate to apparatus and methods for supporting and transferring substrates during photomask fabrication.  
      2. Description of the Related Art  
      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.  
      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 substrate.  
      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.  
      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  
      The present invention generally provides an apparatus to minimize defect formation in a substrate during processing and handling of substrates in a plasma etch chamber by supporting a portion of a substrate in a chamber to minimize contact between the substrate and the chamber components during processing.  
      In one aspect, an apparatus is provided for supporting a substrate including a base plate having an inner perimeter and an outer perimeter, a substrate support member extending horizontally from the inner perimeter of the base plate, at least one substrate support guide extending horizontally from the inner perimeter of the base plate and disposed adjacent the substrate support member, wherein the substrate support member and the at least one substrate support guide are adapted to receive a portion of a substrate.  
      In another aspect, an apparatus is provided for supporting a substrate including a ring, a plurality of spacers disposed on the ring, a plurality of substrate receiving members disposed on the plurality of spacers, wherein the substrate receiving members comprise a base plate having an inner perimeter and an outer perimeter, at least one substrate support guide extending horizontally from the inner perimeter of the base plate and disposed adjacent the substrate support member, wherein the substrate support member and the at least one substrate support guide are adapted to receive a portion of a substrate and the inner perimeter of the base plates are positioned to face an axis of the ring.  
      The apparatus may be used in a loadlock chamber further including one or more walls defining an enclosure, the walls having a sealable loading port selectively sealable by a door and at least one substrate transfer slot selectively sealable by one or more slit valves, the substrate transfer slots disposed substantially opposite of the loading port, at least one substrate support disposed in the enclosure, each substrate support including a ring, a plurality of spacers disposed on the ring, a plurality of substrate receiving members disposed on the plurality of spacers, wherein the substrate receiving members comprise a base plate having an inner perimeter and an outer perimeter, a substrate support member extending horizontally from the inner perimeter of the base plate, and at least one substrate support guide extending horizontally from the inner perimeter of the base plate and disposed adjacent the substrate support member, wherein the substrate support member and the at least one substrate support guide are adapted to receive a portion of a substrate and the inner perimeter of the base plates are position to face an axis of the ring. The loadlock chamber may also be used in a substrate processing system comprising a transfer chamber, at least the one processing chamber coupled to the transfer chamber, and a substrate handler disposed in the transfer chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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.  
       FIG. 1  is a top schematic view of a radial cluster tool for batch processing of semiconductor substrates;  
       FIG. 2  is a perspective view of one embodiment of a loadlock chamber having a substrate support ring disposed therein;  
       FIG. 3  is a perspective view of one embodiment of a substrate support ring; and  
       FIGS. 4A-4G  are schematic views of one embodiment of the substrate support member described herein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Aspects of the invention will be described below in reference to a photolithographic reticle, or photomask, etch system having an inductively coupled plasma etch chamber. The photomask etch system may be a cluster tool similar to that shown in  FIG. 1  is a Centura™ processing system available from Applied Materials, Inc. of Santa Clara, Calif. 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. 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. Although the processes are advantageously performed with the apparatus described herein, the description of the processing chambers and cluster tool is illustrative and should not be construed or interpreted to limit the scope of aspects of the invention.  
       FIG. 1  is a plan view of a vacuum cluster tool  100  suitable for use with the apparatus of the invention described above. The vacuum cluster tool includes multiple substrate processing chambers  112  mounted on a centralized vacuum chamber  114 , such as a transfer chamber, for transferring a substrate from a substrate support in one or more load lock chambers  116 , to one or more process chambers  112 .  
      Transfer of a substrate  218  between the process chambers  112  is typically managed by a substrate handling module, or substrate handier,  118 , preferably with the substrate handling blade  150  mounted thereon. The substrate handler  118  is located in the central transfer chamber  114 . After a substrate is processed, the substrate is retrieved from the processing chambers  112  and transferred to one or more of the load lock chambers  116  and into one or more substrate cassette (not shown) disposed within the one or more load lock chambers  116 . The substrates can then be retrieved from the loadlock chambers  116  and transferred to the next system for additional processing. In photomask manufacturing processing, the process chambers  112  are etching chambers, preferably plasma etching chambers  
       FIG. 2  is a perspective view of one embodiment of a loadlock chamber  116 . The loadlock chamber  116  includes a sidewall  200 , a bottom  204  and a lid (not shown). The sidewall  200  defines a loadlock loading port  208  for loading substrates into and unloading substrates out of the system  100 . Passage  210  is disposed in the sidewall  202  opposite the loading port  208  to allow substrates to be moved from the loadlock chamber  116  into the transfer chamber  114 . Slit valves and slit valve actuators are used to seal the passage  210  and loading port  208  when isolation or staged vacuum is desired. A service port  214  is disposed on one end of the loadlock chamber  116  to provide service and visual access to the loadlock chamber.  116 .  
      A substrate support ring  220  is disposed within the loadlock chamber  116  to support the substrates  218  in a spaced relationship in the loadlock chamber  116  so that a substrate handler  118  can pass between the substrates  218  to place and remove substrates  218  from the loadlock  116 . The substrate support ring  220  preferably supports a plurality of substrates  218  in a vertically displaced arrangement on substrate receiving members  222  disposed on the substrate support ring  220  as shown in  FIGS. 3 and 4 A- 4 E.  
      The substrate receiving members  222  are typically disposed in pairs having an inward facing orientation and are supported in spaced relation by spacers (not shown). The substrate supporting ring  220  may hold a plurality of sets of substrate receiving members  222  and may be vertically disposed from each other at a sufficient distance to allow a substrate handler to position and remove substrates  218  therefrom, such as a distance between about 0.1 inches and about 6 inches, for example, about 0.6 inches to about 0.7 inches apart. In the embodiment shown in  FIG. 2 , two sets of two substrate receiving members are provided on the substrate support ring  220  to support a total of two substrates.  
      The substrate receiving members  222  are adapted to define an opening  217  that a substrate handler blade.  150  can be moved to transfer a substrate with minimal contact between components of the system. An example of a suitable substrate handler blade is described in U.S. Pat. No. 6,537,011 issued on Mar. 25, 2003, and incorporated herein by reference to the extent not inconsistent with the disclosure and claimed aspects herein. While not shown, an actuator may be coupled to the loadlock  116  to raise and lower the loadlock to vertically displace the substrate receiving members  222  to align and receive substrates from a plane of the substrate handler.  
      An on-board vacuum pump (not shown) is mounted on the system  100  adjacent the loadlock chamber  116  and the transfer chamber  114  to pump down the loadlock chamber  116  and the transfer chamber  114 . An exhaust port (not shown) is disposed through the bottom of the loadlock chamber  116  and is connected to the pump via exhaust line. The pump is preferably a high vacuum turbo pump capable of providing milliTorr pressures with very low vibration.  
      Referring to  FIG. 3 , the substrate support ring  220  comprises an annular ring structure  230  having attachment structures  232 , spacers  234 , and substrate receiving members  222  coupled to the spacers  234 . The annular ring structure  230  typically comprises a substantially inert material to processing gases used in the processing chambers, such an inert material may include aluminum or aluminum oxide. The annular ring structure includes an outside perimeter  236  congruent with the inside perimeter of the loadlock chamber for attachment thereto. The annular ring structure  230  may also include one or more attachment structure  232  disposed at the outside diameter for affixation to the inside of the loadlock chamber. The attachment structures  232  of the annular ring structure  230  may be formed in any variable shape to adapt to match any configuration or shape of a loadlock chamber. The inner perimeter  238  of the ring is circular or substantially circular, but may vary on the structure of the loadlock chamber or desires of the operator.  
      Spacers  234  are adapted to be mounted on the annular ring structure  230  and may be further adapted to be mounted on the substrate receiving members  222 . The spacers  234  include one or more apertures for receiving a fastener  235  and may also have one or more protrusion for mating with apertures in the substrate receiving members  222  or annular ring structure  230  surface. Multiple spacers and corresponding substrate receiving members  222  may be aligned and secured by one or more fasteners to provide a stack for receiving more than one substrate. The spacers  234  and the substrate receiving members  222  can form sets that may be repeatedly stacked to form any number vertically displaced sets as the loadlock will physically allow. The spacers  234  and the substrate receiving members  222  are configured on the annular ring structure vertically above or below the plane of the annular ring structure  230  and are configured to define an opening  217  for a substrate handler to position and remove substrates therefrom. The spacers  234  typically provide a spacing of between about 0.1 inches and six inches between substrate receiving members  222  mounted thereon and the ring  230 , for example, the spacer  234  may have a thickness of about 0.625 inches and provide a distance between substrate receiving members of at least that distance  
      The spacers are typically disposed diametrically opposed from each other on the annular ring structure  230 . However, variation in the number and orientation of the spacers  234  may occur for supporting substrates in the loadlock chamber. The spacers are made of a material that is inert or substantially inert with etching gases or processing gases that may contact the spacers, such as aluminum or aluminum oxide, as well as suitable polymers or rubbers.  
      Alternatively, while not shown, the spacers  234  may be adapted to have one or more shelves or lips to provide additional contact surface with the substrate receiving members  222  to help distribute stress or weight when receiving a substrate. The shelf or lip may be a parallel extension of a surface of the spacer  234  that contacts the substrate receiving surface  222 , or alternatively, annular ring structure  230 .  
       FIGS. 4A, 4B , and  4 E are cross-sectional and perspective views of the substrate receiving member  222  of  FIG. 3 . The substrate receiving member  222  includes a base plate  250  having an upper surface  252 , an outer perimeter  254 , and an inner perimeter  256 . The outer perimeter  252  may be co-existing with the outer perimeter  236  of the ring structure  230  and adapted to be coupled with the spacers  234 . The outer perimeter may be further adapted to conform to the shape of portions of the ring structure  230 . The inner perimeter is defined by a substrate support member  260 , at least one substrate support guide  270 , and optionally, one or more recesses  275 , and is adapted to receive a portion of a substrate. The substrate receiving member  222  may comprise a material inert to processing gases, such as aluminum or aluminum oxide. The base plate  250 , a substrate support member  260 , and the at least one substrate support guide  270 , may be individual components coupled together or may be formed from a single piece of material.  
       FIGS. 4C, 4D , and  4 F are partial cross-sectional views of the substrate support member  260 . The substrate support member  260  includes an angular substrate support portion  261 , a vertical support portion  267 , or both. The substrate support member may comprise only angular substrate support portions  261  or only vertical support portions  267 . Generally, a combination of angular substrate support portions  261  and vertical support portions  267  comprise the substrate support member  260 . In one embodiment of the substrate support member  260  includes two portions of the angular support portion  261  disposed on either side of a vertical support portion  267 . The length of the respective portions of the angular substrate support portion  261  and the vertical support portion  267  and the substrate support member  260  may vary. In one example, the substrate support member comprises approximately 4 inches in length with two 0.5 inch angular substrate support portion disposed on either side of a three inch vertical support portion  267 .  
      Referring to  FIGS. 4C and 4F , the angular substrate support portion  261  includes an upper surface  262 , an outer surface  263 , and an inner surface  265 . The inner surface  265  includes an upper substrate aligning surface  264  which is disposed at an incline from the upper surface  262 . The incline may comprise a portion or all of the upper substrate aligning surface  264 . The upper aligning surface  264  may have an angle β from the normal of between about 5° and about 30°, such as 15°. The upper aligning surface  264  provides gravity assisted gross alignment of a substrate  218  received thereon. An example of a substrate aligning surface is disclosed in co-pending U.S. patent application Ser. No. 10/689,783 [Atty. Docket No. APPM/8348], filed on Oct. 21, 2003, and entitled “Mask Etch Processing Apparatus”, which is incorporated herein by reference to the extent not inconsistent with the disclosure and claimed aspects herein.  
      The lower portion  266  of the substrate support member  260  has an inclined surface for receiving the substrate thereon, such as the edge of the substrate. The surface is inclined at an angle a 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 member  260  minimizes the surface area contact between the substrate  218  and the substrate support member  260  as shown in  FIG. 4G . The inclined surface and the lower portion  266  also assist in centering the substrate as it is received thereon.  
      Referring to  FIG. 4D , the vertical support portion  267  includes one or more substantially normal portions having an upper portion  268 , a substantially horizontal lower portion  269 , and a substantially vertical portion  271  disposed between the upper portion  268  and substantially horizontal lower portion  269 . The substantially vertical portion  271  may have an angle of about normal, 90°, to the substantially horizontal lower portion  269 , and alternatively, may have an angle θ up to about 30°, for example, about 15°. The lower portion  269  of the substrate support member  260  has a substantially horizontal surface of about 0°, and alternatively, may have an angle of up to about 5°, for example, about 2.5°. The substrate  218  contacts the substantially horizontal lower portion  269  when supported by the vertical support portion  267 . In a substrate support member  260  having angular support portions  261  and vertical support portions  267 , the substrate  218  has limited or no contact with the substantially horizontal lower surface  269  and the surface area contact between the substrate  218  and the substrate support member  260  is minimized.  
      The substrate receiving member  222  may further comprise one or more substrate support guides  270 . The substrate support guides  270  extend from the base plate  252  along a substantially horizontal plane with the base plate  252 . The substrate support guides are generally formed at the ends of the inner perimeter  256  on either side of the substrate support member  260 . The substrate support guides are adapted to contact or enclose the sides of a substrate  218  positioned on the substrate support member  260  of the substrate receiving member  222 .  
      The substrate support guides include an inner surface  271  and an outer surface  272 . The inner surface  271  has a thickness of approximately the thickness of the base plate  252  and at least a portion up to the complete thickness of the inner surface  271  is angled. The angled surface comprises an inwardly sloping angle θ from the normal of between about 5° and about 30°, such as 15°. In one embodiment of the inner surface  271 , the angled surface has the same angle as the upper aligning surface  264  of the angular support portion  261 . The angled inner surface  271  is believed to further minimize contact with a substrate  218  disposed thereon. Optionally, recesses  275  are disposed between the substrate support guides  270  and the substrate support member  260  to also further minimize contact with a substrate  218  disposed thereon.  
      The substrate support member  260  is generally formed from of an etch resistant, high temperature resistant material, such as aluminum or aluminum oxide, to enable the substrate support member  260  to be used repetitively in the etching process without damage such as scratching or deformation.  
      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.