Abstract:
An apparatus for processing wafer-shaped articles, comprises a closed process chamber providing a gas-tight enclosure. A rotary chuck is located within the closed process chamber, and is adapted to hold a wafer shaped article thereon. A lid is secured to an upper part of the closed process chamber, and comprises a lower surface facing inwardly of the chamber. At least one heating element heats the lower surface of the lid to a desired temperature, so as to prevent condensation of process vapour on the inwardly facing surface of the lid.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to an apparatus for treating surfaces of wafer-shaped articles, such as semiconductor wafers, wherein one or more treatment fluids may be recovered from within a closed process chamber. 
         [0003]    2. Description of Related Art 
         [0004]    Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668. 
         [0005]    Alternatively, a chuck in the form of a ring rotor adapted to support a wafer may be located within a closed process chamber and driven without physical contact through an active magnetic bearing, as is described for example in International Publication No. WO 2007/101764 and U.S. Pat. No. 6,485,531. 
         [0006]    An improved design for closed chamber single wafer wet processing is described in commonly-owned copending application U.S. Pub. No. 2013/0062839, in which a side door permits loading and removal of wafers into and from the process chamber, whereas process liquids and gases may be led into the chamber through a lid secured at the top of the closed process chamber. 
         [0007]    Condensation of process vapors on surfaces of the workpiece or on interior surfaces of the chamber can cause undesired variation in process parameters, and droplets of the condensed liquid may even impact the delicate device structures formed on the workpiece, causing damage and reducing throughput. 
       SUMMARY OF THE INVENTION 
       [0008]    The present inventors have developed an improved method and apparatus for treating wafer-shaped articles, as well as an improved lid for use with such a method and apparatus. 
         [0009]    Thus, the invention in one aspect relates to an apparatus for processing wafer-shaped articles, comprising a closed process chamber, the closed process chamber comprising a housing providing a gas-tight enclosure. A rotary chuck is located within the closed process chamber, the rotary chuck being adapted to hold a wafer shaped article thereon. A lid is secured to an upper part of the closed process chamber, the lid comprising a lower surface facing inwardly of the chamber and at least one heating element for heating the lower surface to a desired temperature. 
         [0010]    In preferred embodiments of the apparatus according to the present invention, the at least one heating element is mounted inside the lid. 
         [0011]    In preferred embodiments of the apparatus according to the present invention, the at least one heating element is mounted so as to be in thermal contact with the lid, such that the lower surface of the lid is heated by the at least one heating element. 
         [0012]    In preferred embodiments of the apparatus according to the present invention, the lid comprises a lower plate that comprises the lower surface and is formed from a chemically-resistant plastic. 
         [0013]    In preferred embodiments of the apparatus according to the present invention, the at least one heating element comprises an electric heating layer. 
         [0014]    In preferred embodiments of the apparatus according to the present invention, the at least one heating element comprises a heat exchange conduit supplied with heated liquid. 
         [0015]    In preferred embodiments of the apparatus according to the present invention, the lid comprises an upper plate formed from a composite fiber-reinforced material and a lower plate that comprises the lower surface and is formed from a chemically-resistant plastic, the at least one heating element being sandwiched between the upper and lower plates. 
         [0016]    In preferred embodiments of the apparatus according to the present invention, the lower plate is formed from a chemically-resistant plastic selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), polyphenylenesulfide (PPS), polyetheretherketone (PEEK), polystyrene/polyethylstyrene (PS/PES), ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), homopolymer of chlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), and ethylene chlorotrifluoroethylene (ECTFE). 
         [0017]    In preferred embodiments of the apparatus according to the present invention, the upper plate is formed from carbon-fiber reinforced plastic. 
         [0018]    In preferred embodiments of the apparatus according to the present invention, the carbon-fiber reinforced plastic comprises a binding polymer selected from the group consisting of epoxy, polyester, vinyl ester and nylon. 
         [0019]    In preferred embodiments of the apparatus according to the present invention, the apparatus also includes a liquid dispenser configured to supply liquid into the closed process chamber at a selected temperature, and at least one temperature sensor positioned so as to detect a temperature within the closed process chamber, and a controller for controlling the at least one heating element so as to maintain the lower surface at a temperature at least 5 K greater than a temperature of heated liquid supplied by the liquid dispenser. 
         [0020]    In another aspect, the present invention relates to a lid for closing a process chamber used for processing wafer-shaped articles, the lid comprising a lower surface facing inwardly of the chamber and at least one heating element for heating the lower surface to a desired temperature. 
         [0021]    In preferred embodiments of the lid according to the present invention, the lid comprises a lower plate that comprises the lower surface and is formed from a chemically-resistant plastic. 
         [0022]    In preferred embodiments of the lid according to the present invention, the at least one heating element comprises an electric heating layer. 
         [0023]    In preferred embodiments of the lid according to the present invention, the at least one heating element comprises a heat exchange conduit supplied with heated liquid. 
         [0024]    In preferred embodiments of the lid according to the present invention, the at least one heating element is mounted inside the lid and in thermal contact with the lid, such that the lower surface of the lid is heated by the at least one heating element. 
         [0025]    In preferred embodiments of the lid according to the present invention, the lid comprises an upper plate formed from a composite fiber-reinforced material and a lower plate that comprises the lower surface and is formed from a chemically-resistant plastic, the at least one heating element being sandwiched between the upper and lower plates. 
         [0026]    In yet another aspect, the present invention relates to a method of wet processing disc-shaped articles, comprising: 
         [0027]    positioning a wafer-shaped article in a process chamber closed by a lid having a lower surface facing downwardly into the process chamber; 
         [0028]    dispensing a heated liquid onto the wafer-shaped article; and heating the lower surface of the lid to a temperature at least 5 k greater than a temperature of the heated liquid. 
         [0029]    In preferred embodiments of the method according to the present invention, the lower surface of the lid is heated by at least one electrical heating element mounted within the lid. 
         [0030]    In preferred embodiments of the method according to the present invention, an internal temperature of the closed process chamber is monitored during dispensing of the heated liquid, and the heating of the lower surface of the lid is controlled on the basis of the monitored temperature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which: 
           [0032]      FIG. 1  is an explanatory cross-sectional side view of a process chamber according to a first embodiment of the invention, with the interior cover shown in its first position; 
           [0033]      FIG. 2  is an explanatory cross-sectional side view of a process chamber according to the first embodiment of the invention, with the interior cover shown in its second position; 
           [0034]      FIG. 3  is a sectional perspective view of an embodiment of a lid according to the present invention; and 
           [0035]      FIG. 4  is a sectional perspective view of another embodiment of a lid according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0036]    Referring now to  FIG. 1 , an apparatus for treating surfaces of wafer-shaped articles according to a first embodiment of the invention comprises an outer process chamber  1 , which is preferably made of aluminum coated with PFA (perfluoroalkoxy) resin. The chamber in this embodiment has a main cylindrical wall  10 , a lower part  12  and an upper part  15 . From upper part  15  there extends a narrower cylindrical wall  34 , which is closed by a lid  36 . 
         [0037]    A rotary chuck  30  is disposed in the upper part of chamber  1 , and surrounded by the cylindrical wall  34 . Rotary chuck  30  rotatably supports a wafer W during use of the apparatus. The rotary chuck  30  incorporates a rotary drive comprising ring gear  38 , which engages and drives a plurality of eccentrically movable gripping members for selectively contacting and releasing the peripheral edge of a wafer W. 
         [0038]    In this embodiment, the rotary chuck  30  is a ring rotor provided adjacent to the interior surface of the cylindrical wall  34 . A stator  32  is provided opposite the ring rotor adjacent the outer surface of the cylindrical wall  34 . The rotor  30  and stator  32  serve as a motor by which the ring rotor  30  (and thereby a supported wafer W) may be rotated through an active magnetic bearing. For example, the stator  32  can comprise a plurality of electromagnetic coils or windings that may be actively controlled to rotatably drive the rotary chuck  30  through corresponding permanent magnets provided on the rotor. Axial and radial bearing of the rotary chuck  30  may be accomplished also by active control of the stator or by permanent magnets. Thus, the rotary chuck  30  may be levitated and rotatably driven free from mechanical contact. Alternatively, the rotor may be held by a passive bearing where the magnets of the rotor are held by corresponding high-temperature-superconducting magnets (HTS-magnets) that are circumferentially arranged on an outer rotor outside the chamber. With this alternative embodiment each magnet of the ring rotor is pinned to its corresponding HTS-magnet of the outer rotor. Therefore the inner rotor makes the same movement as the outer rotor without being physically connected. 
         [0039]    The lid  36  is of an improved design, and comprises an upper plate  50  formed from a composite fiber-reinforced material and a lower plate  60  that faces into the process chamber and is formed from a chemically-resistant plastic, which in this embodiment is ECTFE. Sandwiched between the upper plate  50  and lower plate  60  in this embodiment is a heating element  62 , as shown more clearly in  FIG. 3 . 
         [0040]    Heating element  62  is preferably an electrical heating layer  62  for heating the lower plate  60  to a temperature that prevents condensation of process vapors from occurring on the surface of plate  60  that faces into the process chamber. Electrical heating layer  62  is preferably a silicone rubber heater. 
         [0041]    Lid  36  comprises a central opening  56  through which a process liquid or a rinse liquid may be dispensed onto wafer W at a selected temperature. Temperature sensor  63  positioned so as to detect a temperature within the closed process chamber, and provides its output to a controller (not shown) for controlling the heating element  62  so as to maintain the inwardly facing lower surface of lower plate  60  at a temperature that is at least 5 K greater than a temperature of heated liquid supplied by the liquid dispenser. 
         [0042]    Alternatively, the heating element  62  may be controlled by monitoring the temperature of the heated liquid itself as it is supplied into the process chamber, so as to maintain the inwardly facing lower surface of lower plate  60  at a temperature that is at least 5 K greater than a temperature of heated liquid supplied by the liquid dispenser 
         [0043]    Spacer plate  64  serves to maintain the heater layer  62  pressed into contact with lower plate  60 , as does the annular spacer  66 , which latter element is preferably formed from stainless steel. 
         [0044]    This arrangement is effective to prevent condensation of heated process vapors on the surface of lid  36  that faces into the process chamber, and thereby to prevent the disadvantageous effects of the resulting droplets. 
         [0045]    It will be appreciated that, by heating the inwardly-facing surface of the lid in the manner described above, the heating element  62  does not heat the wafer; therefore, the temperature of the wafer may if desired be independently controlled by a separate heater mounted inside the process chamber. 
         [0046]    The optional stainless steel plate  70  serves to further increase the stiffness of the lid  36  in the region where the lid is traversed by elongated slots  53 . 
         [0047]    Lid  36  may be secured to the process chamber by bolts  57  that pass through bores  58 . 
         [0048]    It will be noted that the wafer W in this embodiment hangs downwardly from the rotary chuck  30 , supported by the gripping members  40 , such that fluids supplied through inlet  56  would impinge upon the upwardly facing surface of the wafer W. 
         [0049]    In case wafer  30  is a semiconductor wafer, for example of 300 mm or 450 mm diameter, the upwardly facing side of wafer W could be either the device side or the obverse side of the wafer W, which is determined by how the wafer is positioned on the rotary chuck  30 , which in turn is dictated by the particular process being performed within the chamber  1 . 
         [0050]    The apparatus of  FIG. 1  further comprises an interior cover  2 , which is movable relative to the process chamber  1 . Interior cover  2  is shown in  FIG. 1  in its first, or open, position, in which the rotary chuck  30  is in communication with the outer cylindrical wall  10  of chamber  1 . Cover  2  in this embodiment is generally cup-shaped, comprising a base  20  surrounded by an upstanding cylindrical wall  21 . Cover  2  furthermore comprises a hollow shaft  22  supporting the base  20 , and traversing the lower wall  14  of the chamber  1 . 
         [0051]    Hollow shaft  22  is surrounded by a boss  12  formed in the main chamber  1 , and these elements are connected via a dynamic seal that permits the hollow shaft  22  to be displaced relative to the boss  12  while maintaining a gas-tight seal with the chamber  1 . 
         [0052]    At the top of cylindrical wall  21  there is attached an annular deflector member  24 , which carries on its upwardly-facing surface a gasket  26 . Cover  2  preferably comprises a fluid medium inlet  28  traversing the base  20 , so that process fluids and rinsing liquid may be introduced into the chamber onto the downwardly facing surface of wafer W. 
         [0053]    Cover  2  furthermore includes a process liquid discharge opening  23 , which opens into a discharge pipe  25 . Whereas pipe  25  is rigidly mounted to base  20  of cover  2 , it traverses the bottom wall  14  of chamber  1  via a dynamic seal  17  so that the pipe may slide axially relative to the bottom wall  14  while maintaining a gas-tight seal. 
         [0054]    An exhaust opening  16  traverses the wall  10  of chamber  1 , and is connected to a suitable exhaust conduit. 
         [0055]    The position depicted in  FIG. 1  corresponds to loading or unloading of a wafer W. In particular, a wafer W can be loaded onto the rotary chuck  30  either through the lid  36 , or, more preferably, through a side door (not shown) in the chamber wall  10 . However, when the lid  36  is in position and when any side door has been closed, the chamber  1  is gas-tight and able to maintain a defined internal pressure. 
         [0056]    In  FIG. 2 , the interior cover  2  has been moved to its second, or closed, position, which corresponds to processing of a wafer W. That is, after a wafer W is loaded onto rotary chuck  30 , the cover  2  is moved upwardly relative to chamber  1 , by a suitable motor (not shown) acting upon the hollow shaft  22 . The upward movement of the interior cover  2  continues until the deflector member  24  comes into contact with the interior surface of the upper part  15  of chamber  1 . In particular, the gasket  26  carried by deflector  24  seals against the underside of upper part  15 , whereas the gasket  18  carried by the upper part  15  seals against the upper surface of deflector  24 . 
         [0057]    When the interior cover  2  reaches its second position as depicted in  FIG. 2 , there is thus created a second chamber  48  within the closed process chamber  1 . Inner chamber  48  is moreover sealed in a gas tight manner from the remainder of the chamber  1 . Moreover, the chamber  48  is preferably separately vented from the remainder of chamber  1 , which is achieved in this embodiment by the provision of the exhaust port  46  opening into the chamber  48 , independently from the exhaust port  16  that serves the chamber  1  in general, and the remainder of the chamber  1  in the  FIG. 2  configuration. 
         [0058]    During processing of a wafer, processing fluids may be directed through medium inlets  56  and/or  28  to a rotating wafer W in order to perform various processes, such as etching, cleaning, rinsing, and any other desired surface treatment of the wafer undergoing processing. 
         [0059]    Provision of the inner chamber  48  within the overall process chamber  1  thus enhances the safety of environmentally closed chambers by permitting the gases and liquids used for wafer processing to be better isolated from the exterior environment of the process chamber, and reduces the risk of process gas, chemical fumes, hot vapor such as vaporized isopropyl alcohol, ozone and the like being released to the tool environment. 
         [0060]    In  FIG. 4 , an alternative lid structure  36 ′ is illustrated, in which the lid  36 ′ does not have the sandwiched structure of the preceding embodiments, but is instead formed of a single principal material, such as stainless steel coated with perfluoroalkyl (PFA) or composite fiber-reinforced material coated with perfluoroalkyl (PFA) or a chemically resistant plastic such as those described above. The lid structure of this embodiment may be used as an alternative to that described in the preceding embodiments, and vice versa. 
         [0061]    Also in this embodiment, the at least one heating element takes the form of a heat exchange conduit  62 ′ supplied with a heat exchange liquid. The other features of the preceding embodiments, such as the temperature sensor and associated control, are not shown in connection with this embodiment, nut it is to be understood that such features may also be included. 
         [0062]    It will be understood that the foregoing description and specific embodiments shown herein are merely illustrative of the invention and the principles thereof, and that modifications and additions may be easily made by those skilled in the art without departing from the spirit and scope of the invention, which is therefore understood to be limited only by the scope of the appended claims.