Abstract:
An apparatus for cleaning a semiconductor wafer is disclosed to substantially improve the efficiency of the cleaning process, and reduce the quantity of cleaning solvent used. The apparatus includes a rotating table for supporting the wafer, a rotation device to rotate the rotation table, a movable or stationary curved-slab for scrubbing the surface of the wafer efficiently, a cleaning nozzle for applying a cleaning solvent or stripper on the surface of the wafer, and a resistance wall for preventing the cleaning solvent spun out from the wafer to pollute the cleaning room.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an apparatus for cleaning a wafer and, more particularly, to an apparatus that may improve the cleaning effect without increasing the amount of solvent used. 
     BACKGROUND OF THE INVENTION 
     As device density in a semiconductor ICs increases control over the semiconductor process conditions is increasingly crucial. In VLSI fabrication, the accurate control of layer thickness, reaction temperature, and pressure is more important for reducing defects in semiconductor ICs. Many materials that are used in semiconductor processes undergo, for example, etching, patterning, and planarization processes after the materials are formed on the semiconductor wafer. Before processes are carried out in a reaction chamber, the wafer will be sent to chemical stages for cleaning of the wafer. The unwanted particles will typically be removed from the wafer during these stages. 
     FIG. 1 shows, in schematic form, a conventional apparatus  10  for removing and cleaning unwanted particles formed on a semiconductor wafer&#39;s surface. The apparatus  10  is used during a cleaning step. The apparatus  10  includes a rotation table  12  for supporting a wafer  14 , and a rotation device  16  to rotate the rotation table. A nozzle  18  is set at top of the wafer  14  to spray cleaning solvent on the surface of the wafer  14 . A resistance wall  20  located surrounding the apparatus  10  is used to prevent the spun out cleaning solvent from polluting the cleaning room. A liquid outlet  22  is located at the bottom of the resistance wall  20  for draining the waste cleaning solvent out of the resistance wall  20 . 
     During the cleaning step, the nozzle  18  sprays cleaning solvent on the surface of the wafer  14  to remove some of the unwanted particles generated on the wafer  14  during the semiconductor processes described above. At this time, the rotation device will rotate the rotation table  12  and wafer  14  according to the predetermined rotation velocity. The kind of rotation will generate centrifugal force to push the cleaning solvent sprayed on the wafer  14  to clean the wafer  14 . After the cleaning step, the cleaning solvent will drain by opening the liquid outlet  22 . However, because of only utilizing the centrifugal force to push the cleaning solvent away from the wafer to clean the wafer  14 , the conventional cleaning apparatus  10  fails to remove a significant amount of the particles especially some particles adhering to the wafer surface tightly. However, the cleaning solvent will be spun out rapidly in the conventional cleaning apparatus  10 , therefore, the cleaning solvent may not stay on the wafer for a long time, which may cause wasteful use of the cleaning agent. 
     SUMMARY OF THE INVENTION 
     In accordance with the background of the invention, the conventional cleaning method utilizing the centrifugal force to push the cleaning solvent away from the wafer in order to clean the wafer will create many drawbacks. Therefore, the present invention provides an apparatus for performing a wafer cleaning that substantially increases the efficiency of the chemical cleaning process without increasing the quantity of cleaning solvent, and reduces contamination to a clean room in fabricating VLSI circuits. 
     In one embodiment, the present invention includes a rotating table supporting the wafer, a rotation device to rotate the rotation table, a movable or stationary curved-slab for scrubbing the surface of the wafer efficiently, a cleaning nozzle for applying a cleaning solvent or stripper on the surface of the wafer, and a resistance wall for preventing the spun out cleaning solvent from polluting the cleaning room. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a schematic diagram of a prior art apparatus used for cleaning a semiconductor wafer; 
     FIG. 2 is a cross-sectional view of an apparatus used for cleaning a semiconductor wafer in accordance with the present invention; 
     FIG. 3 shows a top view of the present invention&#39;s cleaning apparatus of FIG. 2; 
     FIG. 4 shows a cross-sectional view from  1 B— 1 B line of FIG. 3; and 
     FIG. 5 is a cross-sectional view of an apparatus used for cleaning a semiconductor wafer in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Without limiting the spirit and scope of the present invention, the method proposed in the present invention is illustrated with one preferred embodiment about efficiently improving the way in which a wafer is cleaned. People who are knowledgeable about the embodiments, can apply the present invention on different cleaning wafer apparatuses to eliminate the possibility of not removing the particles on the wafer&#39;s surface due to only utilizing the centrifugal force to push the cleaning solvent away from the wafer after cleaning the wafer. The cleaning apparatus of the present invention also may eliminate the disadvantage of wasting cleaning solvent. The usage of the present invention should not be limited by the following embodiments. 
     This cleaning apparatus according to the present invention primarily includes two parts. The first part of this cleaning apparatus utilizes the centrifugal force to push the cleaning solvent away from the wafer to remove particles on the wafer&#39;s surface. The second part is a curved-slab, wherein the shearing stress generated by “slab” can enhance cleaning efficiency. The stripper or cleaning solvent can also be collected by curved-slab, not spun out rapidly. 
     FIG. 2 shows a cross-sectional view of an apparatus  200  for cleaning a semiconductor wafer. The cleaning wafer apparatus  200  includes a rotation portion and a curved-slab portion. The rotation portion further includes a rotating table  201 , a wafer  202  disposed on the rotating table  201 , a rotation device  203  to drive the rotation table  201  and a nozzle  204  connected to the cleaning solvent or stripper outlets (not shown in the figure) and has been set at the top of the wafer  202  to spray cleaning solvent or stripper on the surface of the wafer  202 . The curved-slab portion further includes a holder  301  that is moveable or stationary to support a curved-slab  302  and a resistance wall  205  located surrounding the rotation portion and the curved-slab portion  10  to resist the spun out cleaning solvent that pollutes the cleaning room during the cleaning process. A liquid outlet  206  is used to drain the waste cleaning solvent. A simplified top view of the present invention&#39;s cleaning apparatus  200  is shown in FIG. 3, wherein only the wafer  202 , the nozzle  204  and the curved-slab  302  are shown for conciseness. 
     In this embodiment, the curved-slab  302 , the nozzle  204 , and a rotating wafer  202  deposited on the rotation table  201  are preferably used to remove unwanted fragments generated during the different processes. The cleaning nozzle  204  is set on top of the wafer  202  during the cleaning process. In accordance with the preferred embodiment, the rotation device  203  will rotate the rotation table  12  and wafer  14  when the cleaning process starts. Next, the curved-slab  302  is guided over the wafer  202 , and the cleaning nozzle  204  may spray cleaning solvent or stripper on the surface of the wafer  202 . The nozzle  204  is used to spray deionized (DI) water or chemical solution, such as surfactant, hot alkaline or acidic hydrogen peroxide (H 2 O 2 ) that chemically interacts with the surface of the wafer  202 , in order to achieve better cleanliness and less surface damage. 
     Specifically, in the arrangement of this embodiment, the curved-slab  302 , which is moveable or stationary, is guided near the surface of the wafer  202 . FIG. 4 is a cross-sectional view from  1 B— 1 B line in FIG.  3 . The wafer  202  is moved in the specified direction according to the arrow  420 . And, the curved-slab  302  is set at the top of the wafer  202  which can collect the stripper or cleaning solvent  410 . In accordance the present invention, when the rotation table is rotated, the curved-slab  302  will apply a shearing stress on the wafer  202  because of the relative motion between the curved-slab  302  and the wafer  202 , which will make the fluid direction of the cleaning solvent or stripper in the features (line, hole or trench) of the wafer change. The shearing stress on the wafer  202  may eliminate the possibility of failing to remove the particles on the wafer surface due to only utilizing the centrifugal force to push the cleaning solvent away from the wafer to clean the wafer according to the conventional cleaning apparatus. On the other hand, the cleaning solvent will be spun out rapidly in the conventional cleaning apparatus, therefore, the cleaning solvent may not stop on the wafer for a long time, which may result in wasting cleaning solvent. However, in accordance with the present invention the cleaning solvent  410  may be collected by the curved-slab  302 , not spun out rapidly, which may increase the time that the cleaning solvent stays on the wafer. In short, the curved-slab  302  will apply a shearing stress on the wafer  202  because of the relative motion between the curved-slab  302  and the wafer  202  during the cleaning process, which will make fluid direction of the cleaning solvent  401  not only in the direction of centrifugal force,but also in the shearing direction of stress. Moreover, the curved-slab may increase the time of the cleaning solvent stop on the wafer  202 . Therefore, the present invention may improve the cleaning efficiency. 
     FIG. 5 illustrates the distance relationship between curved-slab  302  and wafer  202 , wherein the distance can be modulated according to the angular velocity of the wafer. For example, the distance between the curved-slab  302  and the wafer  202  may be raised when the angle velocity increases. Therefore, an inclination angle will exist between the curved-slab  302  and the wafer  202  because the angle velocity of the wafer&#39;s edge is larger than the wafer&#39;s center. However, the curve of the curved-slab also can be modulated according to the preferred amount of cleaning solvent to be collected. 
     Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit which is intended to be limited solely by the appended claims.