Abstract:
In a first aspect, a first apparatus is provided. The first apparatus includes (1) a tank adapted to contain fluid; (2) at least one support component mounted in the tank and adapted to support a substrate in a supported position at least partially submerged in the fluid; (3) a transducer adapted to output sonic energy into the fluid; and (4) a reflector positioned at a side of the substrate and adapted to reflect the sonic energy toward an edge of the substrate so as to provide a 100% duty cycle. The reflector is positioned such that the reflector does not obstruct a path employed to load the substrate into the supported position and to unload the substrate from the supported position. Numerous other aspects are provided.

Description:
The present application claims priority from U.S. Provisional Patent Application Ser. No. 60/434,029, filed Dec. 16, 2002, which is hereby incorporated by reference herein in its entirety. 

   BACKGROUND 
   For fabrication of semiconductor devices, thin slices or wafers of semiconductor material require polishing by a process that applies an abrasive slurry to the wafer&#39;s surfaces. A similar polishing step is performed to planarize dielectric or metal films during subsequent device processing on the semiconductor wafer. After polishing, slurry residue is generally cleaned or scrubbed from the wafer surfaces via mechanical scrubbing devices. 
   It is known to provide an apparatus for cleaning a semiconductor wafer in which the wafer is submerged in a fluid, and megasonic energy is directed toward the wafer. However, it would be desirable to improve the cleaning of the edge of the wafer in such an apparatus. 
   SUMMARY OF THE INVENTION 
   In a first aspect of the invention, a first apparatus is provided. The first apparatus includes (1) a tank adapted to contain fluid; (2) at least one support component mounted in the tank and adapted to support a substrate in a supported position at least partially submerged in the fluid; (3) a transducer adapted to output sonic energy into the fluid; and (4) a reflector positioned at a side of the substrate and adapted to reflect the sonic energy toward an edge of the substrate so as to provide a 100% duty cycle. The reflector is positioned such that the reflector does not obstruct a path employed to load the substrate into the supported position and to unload the substrate from the supported position. 
   In a second aspect of the invention, a second apparatus is provided. The second apparatus includes (1) a tank adapted to contain fluid; (2) a plurality of rollers mounted in the tank, including at least one driven roller, and adapted to support a substrate in a supported position at least partially submerged in the fluid while rotating the substrate; (3) a transducer adapted to output sonic energy into the fluid; (4) a first reflector mounted on a first wall of the tank and facing a first side of the substrate and adapted to reflect the sonic energy toward an edge of the substrate; and (5) a second reflector mounted on a second wall of the tank and facing a second side of the substrate and adapted to reflect the sonic energy toward the edge of the substrate. The first and second reflectors are adapted to provide a 100% duty cycle. Additionally, the first and second reflectors are positioned such that the first and second reflectors do not obstruct a path employed to load the substrate into the supported position and to unload the substrate from the supported position. Numerous other aspects are provided, as are methods in accordance with these other aspects of the invention. 
   Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified schematic side view of a wafer cleaning apparatus provided in accordance with the invention; 
       FIG. 2  is a simplified schematic front view of the inventive apparatus of  FIG. 1 ; 
       FIG. 3  is a perspective view of a reflector assembly that is part of the apparatus of  FIG. 1 ; 
       FIG. 4  is a partial cross sectional view of a wafer that is cleaned in the apparatus of  FIG. 1 , showing the edge of the wafer; and 
       FIG. 5  is a side view of an alternative embodiment of the reflector assembly of  FIG. 3 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a simplified schematic side view of a wafer cleaning apparatus  11  provided in accordance with the invention; and  FIG. 2  is a simplified schematic front view of the inventive wafer cleaning apparatus  11 . The inventive apparatus  11  includes a tank  13 , which contains a fluid  15 . An overflow weir  17  maybe associated with an upper portion of the tank  13  to handle fluid  15  which overflows from the tank  13 . Conventional arrangements, which are not shown, may be provided to supply the fluid  15  to the tank  13 , and to remove and/or recycle fluid  15  which overflows into the weir  17 . 
   A wafer W is supported in the tank  13  in a supported position defined by two or more rollers  19  ( FIG. 2 ). The rollers  19  may be provided in accordance with conventional practice to support the wafer W in a vertical orientation, partially or completely submerged in the fluid  15 . Also in accordance with conventional practice, one or more of the rollers  19  may be driven so as to rotate the wafer W while the wafer W is in the supported position. 
   Referring again to  FIG. 1 , a transducer  21  is mounted at a bottom  23  of the tank  13 . The transducer  21  may operate in accordance with conventional practices to output sonic energy, such as megasonic energy, in an upward direction (as indicated by arrows  25 ), into and through the fluid  15 . Conventional arrangements may be provided to energize the transducer  21  and are omitted from the drawing. 
   In accordance with the invention, a first reflector assembly  27  is mounted on a first wall  29  of the tank  13 , and facing a first side  30  of the wafer W. In one or more embodiments of the invention, a second reflector assembly  31  is mounted on a second wall  33  of the tank  13 . It will be observed that the second wall  33  is opposite to the first wall  29 , and that the second reflector assembly  31  faces a second side  35  of the wafer W. The reflector assemblies  27 ,  31  are positioned so as to be set off to respective sides of the wafer W when the wafer W is in the supported position as shown in  FIGS. 1 and 2  on the rollers  19  (which only are shown in  FIG. 2 ). Consequently the reflector assemblies  27 ,  31  do not obstruct a loading path (indicated by arrow  36 ,  FIG. 1 ) by which the wafer W is moved to and removed from the supported position. As a result, the wafer W can be loaded into and removed from the tank  13  without moving the reflector assemblies  27 ,  31  which may be fixedly mounted in the tank  13  as described below. 
     FIG. 3  is a perspective view of a typical one of the reflector assemblies  27 ,  31 . Referring to both  FIGS. 1 and 3 , each of the reflector assemblies  27 ,  31  includes a mounting bracket portion  37  which, for example, may be vertically oriented, and an inclined reflector surface  39  adapted to receive sonic energy from the transducer  21  and direct the sonic energy to an edge of the wafer W. For example, the reflector surface  39  may extend upwardly and outwardly from a bottom edge  41  of the mounting bracket portion  37 . In  FIG. 1 , reference numeral  42  indicates a mounting arrangement adapted to secure the mounting bracket  37  of the second reflector assembly  31  to the wall  33  of the tank  13 . The mounting arrangement  42  may be provided in accordance with conventional practices for mounting components inside megasonic tanks. A similar mounting arrangement (which is not shown to simplify the drawing) may be provided to secure the first reflector  27  to the wall  29  of the tank  13 . In the example shown, the reflector assemblies  27 ,  31  are positioned relative to the supported position of the wafer W, and the reflector surfaces  39  are configured, such that the reflector surfaces  39  reflect the sonic energy  25  output from the transducer  21  toward a lower edge  43  of the wafer W, when the wafer W is in the supported position on the rollers  19  ( FIG. 2 ). 
   Continuing to refer to  FIG. 1 , reference numerals  45  indicate the reflected sonic energy directed from the reflector surfaces  39  to the lower edge  43  of the wafer W. The reflector assemblies  27  and  29  are positioned and adapted so as to provide a 100% cleaning duty cycle for the lower edge  43  of the wafer W. That is, sonic energy is constantly reflected by the reflector surfaces  39  to the edge of the wafer W while the wafer W is in the supported position on the rollers  19 , and the transducer  21  is energized. 
     FIG. 4  is a partial cross sectional view of the wafer W showing the lower edge  43  thereof. As shown in  FIG. 4 , and consistent with conventional practices, the edge  43  of the wafer W may be beveled so as to have bevels  47 . In one or more embodiments of the invention, the reflected sonic energy  45  may be reflected by the reflector surfaces  39  at angles that correspond to the angles of the bevels  47  of the beveled edge  43 . That is, the directions of the reflected sonic energy  45  is substantially parallel to the planes of the bevels  47 . 
   Referring again to  FIG. 1 , the transducer  21  may extend further in a lateral direction relative to the wafer W than transducers that are typically provided in megasonic tanks. For example, the transducer  21  may be arranged so as to extend from a point  49  that is below the reflector surface  39  of the first reflector assembly  27 , to a point  51  that is below the reflector surface  39  of the second reflector assembly  31 . Instead of the single transducer  21  shown in  FIG. 1 , two or more transducers may be provided. For example, three transducers may be provided, including one transducer positioned directly below the supported position of the wafer W and an additional transducer positioned at each one of points  49  and  51 , below the reflector surfaces  39  of the first and second reflector assemblies  27 ,  31 . 
     FIG. 5  is a schematic side view of an alternative reflector assembly  27   a  that maybe substituted for either one or both of the reflector assemblies  27 ,  31  shown in  FIG. 1 . The reflector assemblies shown in  FIGS. 1 and 3  are portrayed such that the reflector surfaces  39  thereof are substantially planar. However, in the alternative reflector assembly  27   a  of  FIG. 5 , the reflector surface  39   a  is curved (e.g., a parabolic curve adapted to focus reflected sonic energy at the lower edge  43  of the wafer W when the wafer W is at its supported position in the tank  13 ). 
   As another alternative, one or both of the reflector assemblies  27 ,  31  could be replaced with a reflector assembly in which the mounting bracket portion  37  extends downwardly from, rather than upwardly from, the reflector surface  39 . According to other alternative arrangements of the reflector assemblies, the reflector surface  39  may be positioned at any point along the height of the mounting bracket  37 . In still another alternative, one or both of the reflector assemblies may be positioned and configured so as to reflect sonic energy to an upper edge  53  of the wafer W when the wafer W is in the supported position in the tank  13 . Similarly, one or both of the reflector assemblies may be positioned and configured to reflect sonic energy to any portion of the wafer W&#39;s edge (e.g., top, bottom, or side edges). Of course, reflector assemblies may be mounted along any of the walls of the tank  13  and be appropriately configured to reflect energy to the wafer W&#39;s edge. 
   In one or more other embodiments of the invention, either one of the reflector assemblies  27 ,  31  may be omitted. 
   The sonic energy output from the transducer  21  and reflected by the reflector assemblies  27 ,  31  may be any type of sonic energy, including megasonic energy, ultrasonic energy or both. 
   If a larger percentage of the wafers perimeter is sought to be contacted by sonic energy, the reflector surface may be sloped or stair stepped so as to maintain the reflector&#39;s focal point on the edge of the wafer. Note that in any embodiment the reflector&#39;s length is preferably chosen so as not to exceed the length wherein the reflector&#39;s focal point contacts the wafer&#39;s edge. Greater lengths may reflect sonic energy that misses the wafer and may cause undesirable sonic turbulence in the tank. 
   Instead of or in addition to the rollers  19 , one or more alternative wafer support components may be provided to support the wafer W at the supported position in the tank  13 . 
   Finally, it will be understood that rather than employing reflectors, transducers may be mounted and configured to direct energy to the wafer&#39;s edge. As previously mentioned, a significant advantage is achieved by positioning the transducer and/or reflector assembly outside the footprint of the supported wafer W. Accordingly, superior edge cleaning may be achieved without the addition of moving parts. 
   While the present invention has been described primarily with reference to wafers, it will be understood that the edge regions of other substrates, such as glass plates employed for flat panel displays, may be similarly cleaned. 
   Accordingly, while the present invention has been disclosed in connection with the preferred embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.