Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 61/006,985 entitled ADJUSTABLE GAP CAPACITIVELY COUPLED RF PLASMA REACTOR INCLUDING LATERAL BELLOWS AND NON-CONTACT PARTICLE SEAL and filed on Feb. 8, 2008, the entire content of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The shrinking feature sizes and the implementation of new materials in next generation of device fabrication have put new requirements on plasma processing equipment. The smaller device features, larger substrate size and new processing techniques (multistep recipes such as for Dual Damascene Etch) have increased the challenge to maintain good uniformity across the wafer for better device yields. 
     SUMMARY 
     An embodiment of a plasma processing apparatus includes a chamber comprising a sidewall surrounding an interior region and having an opening; a cantilever assembly comprising an arm unit extending through the opening of the sidewall and having an outer portion located outside the interior region, and a substrate support on the arm unit and disposed within the interior region; an actuation mechanism coupled to the outer portion of the arm unit and operative to move the cantilever assembly in a vertical direction and bellows arrangement providing a vacuum seal between the arm unit and the sidewall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-C  show an embodiment of an adjustable gap capacitively coupled confined RF plasma reactor including lateral bellows and a non-contact particle seal. 
         FIG. 2  shows an embodiment of a cantilever mounted RF bias housing allowing the lower electrode to translate vertically for an adjustable gap plasma reactor chamber. 
         FIG. 3  illustrates a partial cut away view of an embodiment of the lateral bellows shown in  FIGS. 1A-C . 
         FIG. 4  shows an enlarged detailed of box Q in  FIG. 3  showing details of moveable bellows shield plate and fixed bellows shield. 
         FIGS. 5A and 5B  show partial cross sectional and end views of an embodiment of a labyrinth seal when a lower electrode is in a mid position (medium gap). 
         FIGS. 6A and 6B  show partial cross sectional and end views of the embodiment of  FIGS. 5A and 5B  when the lower electrode is in a low position (large gap). 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A-1C  illustrate an embodiment of an adjustable gap capacitively coupled confined RF plasma reactor  600 . As depicted, a vacuum chamber  602  includes a chamber housing  604 , surrounding an interior space housing a lower electrode  606 . In an upper portion of the chamber  602  an upper electrode  608  is vertically spaced apart from the lower electrode  606 . Planar surfaces of the upper and lower electrodes  608 ,  606  are substantially parallel and orthoganol to the vertical direction between the electrodes. Preferably the upper and lower electrodes  608 ,  606  are circular and coaxial with respect to a vertical axis. A lower surface of the upper electrode  608  faces an upper surface of the lower electrode  606 . The spaced apart facing electrode surfaces define an adjustable gap  610  therebetween. During operation, the lower electrode  606  is supplied RF power by an RF power supply (match)  620 . RF power is supplied to the lower electrode  606  though an RF supply conduit  622 , an RF strap  624  and an RF power member  626 . A grounding shield  636  may surround the RF power member  626  to provide a more uniform RF field to the lower electrode  606 . As described in commonly-owned co-pending U.S. Patent Application Publication No. 2008/0171444, the entire contents of which are herein incorporated by reference, a wafer is inserted through wafer port  682  and supported in the gap  610  on the lower electrode  606  for processing, a process gas is supplied to the gap  610  and excited into plasma state by the RF power. The upper electrode  608  can be powered or grounded. 
     In the embodiment shown in  FIGS. 1A-1C , the lower electrode  606  is supported on a lower electrode support plate  616 . An insulator ring  614  interposed between the lower electrode  606  and the lower electrode Support plate  616  insulates the lower electrode  606  from the support plate  616 . 
     An RF bias housing  630  supports the lower electrode  606  on an RF bias housing bowl  632 . The bowl  632  is connected through an opening in a chamber wall plate  618  to a conduit support plate  638  by an arm  634  of the RF bias housing  630 . In a preferred embodiment, the RF bias housing bowl  632  and RF bias housing arm  634  are integrally formed as one component, however, the arm  634  and bowl  632  can also be two separate components bolted or joined together. 
     The RF bias housing arm  634  includes one or more hollow passages for passing RF power and facilities, such as gas coolant, liquid coolant, RF energy, cables for lift pin control, electrical monitoring and actuating signals from outside the vacuum chamber  602  to inside the vacuum chamber  602  at a space on the backside of the lower electrode  606 . The RF supply conduit  622  is insulated from the RF bias housing arm  634 , the RF bias housing arm  634  providing a return path for RF power to the RF power supply  620 . A facilities conduit  640  provides a passageway for facility components. Further details of the facility components are described in U.S. Pat. No. 5,948,704 and commonly-owned co-pending U.S. Patent Application Publication No. 2008/0171444 and are not shown here for simplicity of description. The gap  610  is preferably surrounded by a confinement ring assembly (not shown), details of which can be found in commonly owned published U.S. Patent Publication No. 2007/0284045 herein incorporated by reference. 
     The conduit support plate  638  is attached to an actuation mechanism  642 . Details of an actuation mechanism are described in commonly-owned co-pending U.S. Patent Publication No. 2008/0171444 incorporated herein by reference. The actuation mechanism  642 , such as a servo mechanical motor, stepper motor or the like is attached to a vertical linear bearing  644 , for example, by a screw gear  646  such as a ball screw and motor for rotating the ball screw. During operation to adjust the size of the gap  610 , the actuation mechanism  642  travels along the vertical linear bearing  644 .  FIG. 1A  illustrates the arrangement when the actuation mechanism  642  is at a high position on the linear bearing  644  resulting in a small gap  610   a .  FIG. 1B  illustrates the arrangement when the actuation mechanism  642  is at a mid position on the linear bearing  644 . As shown, the lower electrode  606 , the RF bias housing  630 , the conduit support plate  638 , the RF power supply  620  have all moved lower with respect to the chamber housing  604  and the upper electrode  608 , resulting in a medium size gap  610   b.    
       FIG. 1C  illustrates a large gap  610   c  when the actuation mechanism  642  is at a low position on the linear bearing. Preferably, the upper and lower electrodes  608 ,  606  remain co-axial during the gap adjustment and the facing surfaces of the upper and lower electrodes across the gap remain parallel. 
     This embodiment allows the gap  610  between the lower and upper electrodes  606 ,  608  in the CCP chamber  602  during multi-step process recipes (BARC, HARC, and STRIP etc.) to be adjusted, for example, in order to maintain uniform etch across a large diameter substrate such as 300 mm wafers or flat panel displays. In particular, this embodiment pertains to a mechanical arrangement to facilitate the linear motion necessary to provide the adjustable gap between lower and upper electrodes  606 ,  608 . 
       FIG. 1A  illustrates laterally deflected bellows  650  sealed at a proximate end to the conduit support plate  638  and at a distal end to a stepped flange  628  of chamber wall plate  618 . The inner diameter of the stepped flange defines an opening  612  in the chamber wall plate  618  through which the RF bias housing arm  634  passes. 
     The laterally deflected bellows  650  provides a vacuum seal while allowing vertical movement of the RF bias housing  630 , conduit support plate  638  and actuation mechanism  642 . The RF bias housing  630 , conduit support plate  638  and actuation mechanism  642  can be referred to as a cantilever assembly. Preferably, the RF power supply  620  moves with the cantilever assembly and can be attached to the conduit support plate  638 .  FIG. 1B  shows the bellows  650  in a neutral position when the cantilever assembly is at a mid position.  FIG. 1C  shows the bellows  650  laterally deflected when the cantilever assembly is at a low position. 
     A labyrinth seal  648  provides a particle barrier between the bellows  650  and the interior of the plasma processing chamber housing  604 . A fixed shield  656  is immovably attached to the inside inner wall of the chamber housing  604  at the chamber wall plate  618  so as to provide a labyrinth groove  660  (slot) in which a movable shield plate  658  moves vertically to accommodate vertical movement of the cantilever assembly. The outer portion of the movable shield plate  658  remains in the slot at all vertical positions of the lower electrode  606 . 
     In the embodiment shown, the labyrinth seal  648  includes a fixed shield  656  attached to an inner surface of the chamber wall plate  618  at a periphery of the opening  612  in the chamber wall plate  618  defining a labyrinth groove  660 . The movable shield plate  658  is attached and extends radially from the RF bias housing arm  634  where the arm  634  passes through the opening  612  in the chamber wall plate  618 . The movable shield plate  658  extends into the labyrinth groove  660  while spaced apart from the fixed shield  656  by a first gap (channel “B” in  FIG. 4 ) and spaced apart from the interior surface of the chamber wall plate  618  by a second gap (channel “C” in  FIG. 4 ) allowing the cantilevered assembly to move vertically. The labyrinth seal  648  blocks migration of particles spalled from the bellows  650  from entering the vacuum chamber interior  605  ( FIG. 2 ) and blocks radicals from process gas plasma from migrating to the bellows  650  where the radicals can form deposits which are subsequently spalled. 
       FIG. 1A  shows the movable shield plate  658  at a higher position in the labyrinth groove  660  above the RF bias housing arm  634  when the cantilevered assembly is in a high position (small gap  610   a ).  FIG. 1C  shows the movable shield plate  658  at a lower position in the labyrinth groove  660  above the RF bias housing arm  634  when the cantilevered assembly is in a low position (large gap  610   c ).  FIG. 1B  shows the movable shield plate  658  in a neutral or mid position within the labyrinth groove  660  when the cantilevered assembly is in a mid position (medium gap  610   b ). While the labyrinth seal  648  is shown as symmetrical about the RF bias housing arm  634 , in other embodiments the labyrinth seal  648  may be asymmetrical about the RF bias arm  634 . 
       FIG. 2  shows an embodiment of components of a cantilever assembly in an adjustable gap capacitively coupled confined RF plasma reactor. The components are shown partially cut away and without other components for ease of description. In the illustration, the RF bias housing  630  is supported inside the vacuum chamber  602  by conduit support plate  638  located outside the chamber. A proximate end of the RF bias housing arm  634  is attached to the conduit support plate  638 . Service openings in the conduit support plate  638  allow access to the facilities conduit  640  and RF supply conduit  622  which pass axially through the interior of the RF bias housing arm  634  to the space behind the lower electrode  606 . The RF supply conduit  622  and facilities conduit  640  are at a first pressure such as atmospheric pressure and the interior of the vacuum chamber  602  is at a second pressure such as a reduced pressure by connection to a vacuum pump through a vacuum portal  680 . The bellows  650  provides a vacuum seal while allowing vertical movement of the cantilever assembly. 
     The conduit support plate  638  is attached to the actuation mechanism  642  which travels vertically up and down relative to the vacuum chamber  602  along linear bearing  644 . The linear bearing  644  is attached to the chamber wall plate  618  which provides a sidewall of the vacuum chamber  602 . The chamber wall plate  618  does not move during operation of the actuation mechanism  642 , but may be releasably attached to the vacuum chamber  602  to facilitate removal and insertion of the RF bias housing  630  and lower electrode assembly in the vacuum chamber  602 . When the actuation mechanism  642  travels vertically relative to the vacuum chamber  602 , the conduit support plate  638 , and RF bias housing  630  also travel vertically in the direction indicated by arrows A-A′ in  FIG. 2 . 
     The chamber wall plate  618  has stepped flange  628  forming an opening into the chamber housing  604 . The RF bias housing arm  634  passes into the interior of chamber housing  604  through the opening  612  defined by the inner diameter of the stepped flange  628 . An inner diameter of the stepped flange  628  defining the opening  612  is larger than an outside transverse dimension of the RF bias housing arm  634  to allow the arm  634  to move in the vertical direction A-A′. A proximate end of the RF bias housing arm  634  attaches and seals to the conduit support plate  638  in a manner such that the RF bias housing arm  634  may move vertically relative to the chamber wall plate  618 . The bellows  650  creates a vacuum seal to seal the proximate end of the RF bias housing arm  634  to the chamber wall plate  618  as will now be described with reference to  FIG. 3 . 
       FIG. 3  shows the bellows  650  forming a transversely movable vacuum seal between the proximate end of the RF bias housing arm  634  and the chamber wall plate  618 . An accordion appearance of the bellows  650  is not shown here. Details of bellows  650  are described further in commonly-owned co-pending U.S. Patent Application Publication No. 2008/0171444. A proximate end  650   a  of the bellows  650  is clamped beneath a clamp edge  654  of the RF bias housing arm  634  with an O-ring to sandwich a smaller diameter end of the proximate end  650   a , between the clamp edge  654  and the conduit support plate  638 . The larger diameter distal end  650   b  of bellows  650  is clamped beneath a clamp ring  652  to form a seal against the outside wall of the chamber wall plate  618  around a periphery of the opening  612  adjacent the inside diameter of the stepped flange  628 . The clamp ring  652  is preferably bolted to the chamber wall plate  618 . 
     The bellows  650  is substantially isolated from the vacuum chamber  602  interior by labyrinth seal  648  (see box “Q” in  FIG. 3  and  FIG. 4 ). The movable shield plate  658  extends radially from the RF bias housing arm  634  and moves vertically with the cantilever assembly. A recess around the periphery of the stepped flange  628  inner diameter on an interior surface of the chamber wall plate  618  is covered by fixed shield  656  defining the labyrinth groove  660  between the interior wall of the chamber wall plate  618  and the fixed shield  656 . The movable shield plate  658  extends into the labyrinth groove  660  with a gap on either side of the movable shield plate  658  such that the movable shield plate  658  is positioned in the labyrinth groove  660  spaced apart from the walls of the labyrinth groove  660 . Thereby, the movable shield plate  658  can move vertically within the labyrinth groove  660  without making contact with any surface defining the labyrinth groove  660 . As depicted in  FIG. 4 , such a positioning of the labyrinth groove  660  creates an annular channel “B” between the fixed shield plate  656  and the movable shield plate  658  and a second channel “C” between the movable shield plate  658  and the surface of the chamber wall plate  618 . 
     The labyrinth seal  648  substantially blocks particle migration between the interior  686  of the lateral bellows and the vacuum chamber interior  605  under vacuum processing conditions. Preferably, a ratio of a thickness of the channels “B” and “C” in the labyrinth groove  660  to a depth that the moveable shield plate  658  protrudes into the labyrinth groove  660  is in a range of about 1:8 to about 1:50. For example, the “B” and “C” channel thicknesses are the size of the gap between the movable shield plate  658  and the chamber wall plate  618  on the one side and the fixed shield plate  656  on the other. 
       FIG. 5A  illustrates a longitudinal cross section and  FIG. 5B  illustrates a transverse view from the interior of the vacuum chamber  602 , of an embodiment of the labyrinth seal  648  when the cantilever assembly is in a mid or neutral position (medium gap  610   b ). The RF bias housing arm  634  passes through the opening in the chamber wall plate  618  defined by the inner diameter of the stepped flange  628 . The movable shield plate  658  is narrower than the labyrinth groove  660  such that an outer edge of the movable shield plate  658  penetrates the labyrinth groove  660  to make a non-contact particle seal between the interior  686  of the bellows  650  and the vacuum chamber interior  605 . The movable shield plate  658  may be bolted to the RF bias housing arm  634  by bolts  692  or attached by a removable adhesive or the like. The fixed shield  656  may be bolted to the interior surface of the chamber wall plate  618  by bolts  690  or attached by an adhesive or other detachable joint or the like. 
       FIG. 6A  illustrates a longitudinal cross section and  FIG. 6B  illustrates a transverse view from the interior of the vacuum chamber  602 , of the embodiment of the labyrinth seal  648  shown in  FIGS. 5A and 5B  when the cantilever assembly is in a low position (large gap  610   c ). As depicted, the fixed shield  656  may be made up of several sections to allow installation and removal of the fixed shield  656  and installation and removal of the movable shield plate  658 . For example, the fixed shield plate  656  includes a lower fixed shield portion  657  and an upper fixed shield portion  659 . 
     While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.

Technology Category: h