Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to manufacturing of semiconductor materials and the portion related to chemical mechanical planarization (CMP). More specifically, the present invention provides for reduction of the wafer lift-off force on a CMP tool, and thereby diminishing the chances of wafer breakage.  
         [0003]     2. Background Art  
         [0004]     In the field of semiconductor manufacturing, one of many steps of manufacturing includes the planarization of the semiconductor wafers. This is typically done via chemical mechanical planarization (CMP) tools. A primary goal of the CMP tooling step is to essentially polish a surface of the wafer so as to render it both planar and smooth.  
         [0005]      FIG. 1  depicts a typical CMP tool system  10  wherein a wafer  8  is held face down on a carrier  20  that rotates (about arrow  22 ), and is pressed against a polishing pad  2  attached on a rotating disk  4 , or platen. Various liquids and/or slurries (e.g., colloidal silica) (not shown) are continuously fed to a platen/wafer interface  6  to aid in this polishing. Upon satisfactory completion of the polishing step, the polished wafer  8  is removed from the interface  6 , specifically, and from the CMP tool system  10 , in general, by applying a lift-off force F 0 .  
         [0006]     A shortcoming in the current art is that, often, upon lift off of wafer  8  from pad  2  and platen  4  breakage of wafer  8  occurs. Breakage occurs because the mechanical lift-off force (i.e., F 0 ) necessary can at times exceed the fracture strength of wafer  8 . The lift-off force F 0  is high for various reasons, including the flatness and smoothness of both the polished wafer  8  and polishing pad  2 . Necessary lift-off force F 0  may be increased further by drag due to rinsing water (not shown) on polishing pad  2 . Surface tension at interface  6  and atmospheric pressure further effects necessary lift-off force F 0 , as well.  
         [0007]     CMP tools that include fixed abrasive polishing pads  2  are particularly prone to wafer  8  breakage because the smooth texture of polishing pads  2  causes very high requisite lift-off forces F 0 . Currently, spinning, sweeping, or blowing water off polishing pad  2  just prior to lift-off is used in an attempt to make wafer  8  lift-off more benign and successful. While effective at allowing successful lift-off of wafer  8 , these methods increase the likelihood of scratching wafer  8 , which is undesirable.  
         [0008]     In view of the foregoing, there exists a need for an improvement in CMP technique that reduces wafer removal breakage.  
       SUMMARY OF THE INVENTION  
       [0009]     In general, methods and a system of reducing wafer removal force on a chemical mechanical planarization (CMP) tool are disclosed.  
         [0010]     A first aspect of the present invention provides a method of reducing wafer removing force on a chemical mechanical planarization (CMP) tool, comprising the steps of: planarizing a wafer on a platen at a wafer/platen interface; applying carbonated water to the wafer/platen interface to reduce the removing force; and removing the wafer from the platen.  
         [0011]     A second aspect of the present invention provides a system for reducing wafer removing force on a chemical mechanical planarization (CMP) tool, comprising: means for planarizing a wafer on a platen at a wafer/platen interface; means for applying carbonated water to the wafer/platen interface; and means for removing wafer from platen.  
         [0012]     A third aspect of the present invention provides a method of reducing wafer removing force on a chemical mechanical planarization (CMP) tool, comprising the steps of: planarizing a wafer on a platen at a wafer/platen interface; applying pressurized carbonated deionized water that is between approximately 40 and 50 degrees Fahrenheit to the wafer/platen interface, to reduce wafer removing force; and removing the wafer from the platen. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings in which:  
         [0014]      FIG. 1  depicts an elevation view of a chemical mechanical planarization (CMP) system in the related art.  
         [0015]      FIG. 2  depicts an elevation view of one embodiment of a CMP system, in accordance with the present invention.  
         [0016]      FIG. 3  depicts a close up elevation view of a wafer/platen interface of  FIG. 2 , in accordance with the present invention. 
     
    
       [0017]     The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements.  
       DETAILED DESCRIPTION  
       [0018]     As indicated above, the present invention provides methods and a system for reducing wafer removing force on a chemical mechanical planarization (CMP) tool.  
         [0019]      FIG. 2  shows a CMP tool system  100  in accordance with one embodiment of the present invention. A pad  12  resides on a platen  14 . Held in a face down configuration, a wafer  18  is rotated against pad  12  so as to polish wafer  18 .  
         [0020]     Upon completion of polishing wafer  18  but prior to liftoff of wafer  18  from pad  12  and platen  14 , carbonated water  25  is applied at interface  16  between wafer  18  and platen  14  (and pad  12 ). Carbonated water  25  may be applied, for example, via an applicator(s)  30  (e.g., nozzle) in fluid communication with a reservoir  31  and pump  32 . Other suitable means now known or later developed may be utilized to provide and apply carbonated water  25  to interface  16 .  
         [0021]     In one embodiment, carbonated water  25  may be deionized carbonated water  25  and may be pressurized so as to be at a higher pressure than the pressure that is ambient. Similarly, carbonated water  25  may be colder than ambient temperature, and may be chilled prior to application, for example, to a temperature in the range of approximately 40-50° Fahrenheit. For example, relative motion of pad  12  and wafer  18 , prior to application of carbonated water  25 , may cause a warming of a temperature in area of interface  16 . As the close-up view in  FIG. 3  depicts, carbonated water  25  has been placed at interface  16  between wafer  18  and pad  12  (and platen  14 ).  
         [0022]     Bubbles  26  of carbon dioxide (CO 2 ) gas form in interface  16  between wafer  18  and platen  14  from carbonated water  25 . As bubbles  26  of carbon dioxide gas form and as the temperature of carbonated water  25  increases, due to ambient temperature being warmer than carbonated water  25 , bubbles  26  increase in size. Force F B  is exerted against surface  13  of pad  12  and surface  19  of wafer  18 , thereby decreasing the necessary lift-off force F 1  that is ultimately required to subsequently lift wafer  18  from pad  12  and platen  14 . The carbon dioxide gas formed between wafer  18  and platen  14  reduces the force on wafer  18  by reducing the atmospheric effect due to partial vacuum that is created during lift-off. Thus, ultimately lift-off force F 1  required is less than F 0  ( FIG. 1 ) (i.e., without using carbonated water  25 ) so that wafer  18  breakage is less likely to occur. A removal mechanism  40  in communication with wafer  18  is used to remove wafer  18  from platen  14  by exerting requisite force to wafer  18 . The removal mechanism  40  may, for example, include a motor or other suitable means now known or later developed to provide adequate force to removed wafer  18  from platen  14 .  
         [0023]     The foregoing description of the preferred embodiments of this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.

Technology Category: 5