Abstract:
An apparatus for processing wafer-shaped articles comprises a spin chuck for holding a wafer-shaped article in a predetermined orientation, and a rotating shower head for supplying process gas to a surface of a wafer-shaped article when held by the spin chuck. The rotating shower head comprises an outlet plate having plural openings formed in each of a central and a peripheral region thereof. A process gas feed is provided so as to supply process gas to a gas distribution chamber. The gas distribution chamber is in fluid communication with a plurality of openings formed in the shower head.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to an apparatus for processing wafer-shaped articles, such as semiconductor wafers, and more particularly relates to such an apparatus comprising a spin chuck and a rotating gas showerhead. 
         [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]    It is known to equip such chucks with a gas showerhead so as to introduce a controlled atmosphere adjacent a surface of the wafer undergoing processing on the chuck. 
         [0007]    Examples of such showerheads are shown in commonly-owned copending application US 2014/0026926 and commonly-owned U.S. Pat. No. 8,926,788. However, depending upon the type of chuck and the type of surrounding structure, it can be difficult to maintain a desired atmosphere and it can also be difficult to utilize process gas efficiently with conventional gas showerheads. 
       SUMMARY OF THE INVENTION 
       [0008]    The present inventors have developed an improved apparatus for treatment of wafer-shaped articles, in which a spin chuck is mounted in relation to a rotating gas showerhead. 
         [0009]    Thus, in one aspect, the present invention relates to an apparatus for processing wafer-shaped articles, comprising a spin chuck for holding a wafer-shaped article in a predetermined orientation, and a rotating shower head for supplying process gas to a surface of a wafer-shaped article when held by the spin chuck. The rotating shower head comprises an outlet plate having plural openings formed in each of a central and a peripheral region thereof. A process gas feed is provided so as to supply process gas to a gas distribution chamber. The gas distribution chamber is in fluid communication with a plurality of openings formed in the shower head. 
         [0010]    In preferred embodiments of the apparatus according to the present invention, the outlet plate is affixed to the spin chuck and covers a central region thereof. 
         [0011]    In preferred embodiments of the apparatus according to the present invention, each of the plural openings has a cross-sectional area in a range from 0.3 to 2.0 mm 2 , preferably from 0.5 to 1.5 mm 2 , and more preferably from 0.7 to 1.2 mm 2 . In preferred embodiments of the apparatus according to the present invention, the plural openings includes at least 50 of the openings, and preferably at least 80 of the openings. 
         [0012]    In preferred embodiments there is a plurality of outermost openings arranged in the transition between chuck and outlet plate so that liquid that might be present in the gas distribution chamber will be discharged through such outermost openings. 
         [0013]    In preferred embodiments of the apparatus according to the present invention, the plural openings are inclined so as to direct fluid passing from the gas distribution chamber through the plural openings radially outwardly of the spin chuck. 
         [0014]    In preferred embodiments of the apparatus according to the present invention, the outlet plate is domed such that a central region thereof is positioned farther from a wafer-shaped article when positioned on the spin chuck than a peripheral region thereof. 
         [0015]    In preferred embodiments of the apparatus according to the present invention, the outlet plate is formed of a ceramic material. 
         [0016]    In preferred embodiments of the apparatus according to the present invention, the outlet plate is formed in one piece with at least a ring part of the spin chuck. 
         [0017]    In preferred embodiments of the apparatus according to the present invention the inwardly facing annular surface of the spin chuck is inclined (upwardly or downwardly) so that liquid adhering thereto will be either upwardly or downwardly transported when the spin chuck spins. 
         [0018]    In preferred embodiments of the apparatus according to the present invention, the spin chuck arranged within a chamber. 
         [0019]    In preferred embodiments of the apparatus according to the present invention, the chamber is a closed chamber. 
         [0020]    In preferred embodiments of the apparatus according to the present invention, the spin chuck is a magnetic rotor, and the apparatus further comprises a magnetic stator surrounding the magnetic rotor. 
         [0021]    In another aspect, the present invention relates to an apparatus for processing wafer-shaped articles, comprising a spin chuck for holding a wafer-shaped article in a predetermined orientation, and a rotating shower head for supplying process gas to a surface of a wafer-shaped article when held by the spin chuck. A process gas feed is provided so as to supply process gas to a gas distribution chamber. The gas distribution chamber is in fluid communication with a plurality of openings formed in the shower head. The spin chuck is a magnetic rotor, and the apparatus further comprises a magnetic stator surrounding the magnetic rotor. 
         [0022]    In preferred embodiments of the apparatus according to the present invention, the rotating shower head comprises an outlet plate having discharge openings formed therein, the outlet plate being affixed to the magnetic rotor and covering a central region thereof. 
         [0023]    In preferred embodiments of the apparatus according to the present invention, the outlet plate is domed such that a central region thereof is positioned farther from a wafer-shaped article when positioned on the spin chuck than a peripheral region thereof. 
         [0024]    In preferred embodiments of the apparatus according to the present invention, the spin chuck is arranged within a closed chamber comprising a top wall having a peripheral region positioned above the magnetic rotor and a central region that extends downwardly within the magnetic rotor, and wherein an inner surface of the top wall and the outlet plate define the gas distribution chamber. 
         [0025]    In preferred embodiments of the apparatus according to the present invention, the top wall is stationary. 
         [0026]    In preferred embodiments of the apparatus according to the present invention, a blocking gas feed is provided so as to supply blocking gas to a gap defined between a peripheral surface of the magnetic rotor and an inner surface of the chamber, the gap being positioned so as to confine process gas within the gas distribution chamber. 
         [0027]    In preferred embodiments of the apparatus according to the present invention, a gas injection head is positioned in the top wall and passing through a central opening in the outlet plate. 
         [0028]    In preferred embodiments of the apparatus according to the present invention, the rotating shower head comprises a central opening through which liquid can be supplied towards the wafer shaped article. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    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: 
           [0030]      FIG. 1  is an explanatory cross-sectional side view of an apparatus according to a first embodiment of the invention; 
           [0031]      FIG. 2  is a plan view of the outlet plate of the gas showerhead used in the embodiment of  FIG. 1 ; 
           [0032]      FIG. 3  is an explanatory cross-sectional side view of an apparatus according to a second embodiment of the invention; and 
           [0033]      FIG. 4  is an enlarged view of the detail IV in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0034]    Referring now to  FIG. 1 , an apparatus for treating surfaces of wafer-shaped articles according to a first embodiment of the invention comprises a closed process chamber  13 , in which is arranged an annular spin chuck  16 . Spin chuck  16  is a magnetic rotor that is surrounded by a magnetic stator  17  positioned outside the chamber, so that the magnetic rotor is freely rotating and levitating within the chamber  13  without touching the chamber walls. The chamber  13  is closed at its upper end by lid  14  rigidly secured thereto. 
         [0035]    Further structural details of such a magnetic rotor chuck are described, for example, in commonly-owned U.S. patent application publication no. 2013/0134128. 
         [0036]    The annular spin chuck  16  has a circular series of downwardly-depending gripping pins  19 , which releasably hold a wafer W during processing. A lower dispense unit  22  is provided so as to supply liquid and/or gas to the side of the wafer W that faces downwardly within chamber  13 . A heater  31  is disposed within the chamber  13 , so as to heat the wafer W to a desired temperature depending upon the process being performed. Heater  31  preferably comprises a multitude of blue LED lamps, whose radiation output tends to be absorbed preferentially by silicon wafers relative to the components of the chamber  13 . 
         [0037]    An upper dispense unit comprises an outer gas conduit  27  and an inner liquid conduit  25  arranged coaxially within the outer gas conduit  25 . Conduits  25 ,  27  both traverse the lid  14 , and permit liquid and gas to be supplied to the side of the wafer W that faces upwardly within chamber  13 . 
         [0038]    A gas showerhead is delimited at its lower side by an outlet plate  28 , which is also shown in plan view in  FIG. 2 . The outlet plate  28  comprises a multitude of discharge orifices  29 , which permit process gas to pass out of the gas showerhead from the gas distribution chamber  37  to the region adjacent the upwardly facing side of the wafer W. The discharge orifices  29  in this embodiment each have a cross-sectional area in a range from 0.3 to 2.0 mm, preferably from 0.5 to 1.5 mm, and more preferably from 0.7 to 1.2 mm. There are preferably at least 20 orifices  29 , and more preferably at least 80; even more preferably 300. 
         [0039]    The outlet plate  28  is rigidly secured to the spin chuck  16 , and therefore rotates along with the spin chuck  16 . On the other hand, the conduits  25 ,  27  are stationarily mounted in the lid  14  of chamber  13 , and pass with a slight clearance through a central opening formed in the plate  28 . 
         [0040]    As shown in  FIG. 2 , there are a plurality of these orifices  29  in each of a central region and a peripheral region of the plate  28 , wherein the central region is defined as being the area within the half-radius  30  of the plate  28 , and the peripheral region is defined as being the area outside of the half-radius  30 . 
         [0041]    Returning to  FIG. 1 , it will be seen that the gas distribution chamber  37  is supplied with process gas through a process gas supply conduit  34 , which in turn communicates with a source of process gas (not shown), which in preferred embodiments is ozone. 
         [0042]    The lid  14  of chamber  13  is also traversed by one or more nozzles  40  that are supplied with purge, or blocking, gas, which in this embodiment is preferably nitrogen gas. A more detailed description of possible constructions of a lid incorporating such nozzles is set forth in commonly-owned copending published application US 2013/0134128, as well as in commonly-owned copending application Ser. No. 14/145,241. 
         [0043]    The blocking gas supplied through nozzles  40  performs an important function in this embodiment, in that it serves to confine the process gas within the gas distribution chamber such that the process gas delivered through the one or more nozzles  34  passes more completely through the orifices  29  of plate  28 , and is largely prevented from escaping through the annular gap between the outer periphery of chuck  16  and the inner surface of chamber wall  13 . 
         [0044]    On the other hand, experiments conducted by the inventors had shown that, in the absence of supplying such blocking gas, a large proportion of the process gas, in some instances a majority thereof, escaped through the gap between the outer periphery of the magnetic rotor and the chamber wall, such that the process gas was exhausted from the chamber through exhaust  46  without having been brought into contact with the upwardly-facing side of the wafer W. 
         [0045]    The dashed line  43  in  FIG. 1  shows the approximate location of the boundary formed between the process gas and the blocking gas thanks to the structure shown in this embodiment. The provision of a gas-gas boundary to confine the process gas within the distribution chamber  37  is an innovative solution in the context of a magnetic rotor chuck, which does not contact the chamber in which it is mounted and which therefore cannot be equipped with conventional gas seals. 
         [0046]    Turning now to  FIGS. 3 and 4 , another embodiment of the invention is shown that includes several features that were found to further improve the efficiency of the process gas supply through chamber  37  and into the target region adjacent the upwardly facing side of the wafer W. 
         [0047]    Specifically, the outlet plate  28  in the  FIGS. 3 and 4  embodiment is domed upwardly, such that its central region is more distant from the wafer W than its peripheral region. Conversely, the lid  14  of the chamber  13  is reconfigured, such that an intermediate region thereof extends downwardly into the region surrounded by the magnetic rotor  16 . The axial extent of the gas distribution chamber  37  is thereby significantly reduced relative to the embodiment of  FIGS. 1 and 2 , which the inventors have found further improves the efficiency of process gas supply. 
         [0048]    Additionally, as shown in  FIG. 3 , the discharge orifices  29  of this embodiment are oriented at an oblique angle relative to the vertical axis of rotation of the spin chuck  16 , such that the orifices are directed radially outwardly of the spin chuck  16 . The inventors have found that this configuration helps to divert any liquids in the distribution chamber  37  away from the upwardly facing surface of wafer W, while permitting the process gas supplied through conduit  34  still to reach the target region adjacent the wafer W. 
         [0049]    While the present invention has been described in connection with various preferred embodiments thereof, it is to be understood that those embodiments are provided merely to illustrate the invention, and that the invention is not limited to those embodiments, but rather includes that which is encompassed by the true scope and spirit of the appended claims.