Apparatus and method for sequentially polishing and loading/unloading semiconductor wafers

Abstract

A chemical mechanical polishing (CMP) apparatus and method for polishing semiconductor wafers utilizes multiple wafer carriers that are transferred to different positions about a polishing pad to polish at least one semiconductor wafer while another semiconductor wafer is being loaded onto or unloaded from one of the wafer carriers. The different positions include multiple polishing positions and one or more loading/unloading positions. In some embodiments, the CMP apparatus is configured such that a semiconductor wafer is polished at a loading/unloading position. The CMP apparatus may also be configured to continuously polish one or more semiconductor wafers while the wafer carriers are being transferred to different positions. Thus, the CMP apparatus can continuously process the semiconductor wafers without significant idle periods. Consequently, in these embodiments, the efficiency of the CMP apparatus is significantly increased. Furthermore, the wafer carriers of the CMP apparatus are preferably restricted to a small area to decrease the footprint of the apparatus.

1 . An apparatus for polishing surfaces of objects comprising: 
 a polishing pad having a polishing surface;    a plurality of object carriers, said object carriers being configured to secure said objects to be polished; and    a carrier transfer assembly that is configured to sequentially transfer each of said object carriers to different positions on said polishing pad to polish said objects exclusively on said polishing surface of said polishing pad, said carrier transfer assembly being further configured to independently move each of said object carriers such that a first object can be polished by a first object carrier of said object carriers and a second object can be loaded onto a second object carrier of said object carriers in a substantially parallel manner.    
     
     
         2 . The apparatus of  claim 1  further comprising a first object transport device that sequentially transports said objects to said object carriers when said object carriers are transferred to a first location that is associated with a first position of said different positions.  
     
     
         3 . The apparatus of  claim 2  wherein said first object transport device is configured to sequentially transport said objects from said object carriers when said object carriers are situated at said first location.  
     
     
         4 . The apparatus of  claim 2  wherein said first location laterally coincides with said first position of said different positions.  
     
     
         5 . The apparatus of  claim 2  wherein said apparatus further includes a second object transport device that sequentially transports said objects from said object carriers when said object carriers are transferred to a second location associated with a second position of said different positions.  
     
     
         6 . The apparatus of  claim 5  wherein said second location laterally coincides with said second position of said different positions.  
     
     
         7 . The apparatus of  claim 1  further comprising a first object transfer station that is situated adjacent to said polishing pad to transfer said objects to said object carriers for polishing.  
     
     
         8 . The apparatus of  claim 7  wherein said first object transfer station includes a thickness detection device to measure the thickness of said objects.  
     
     
         9 . The apparatus of  claim 7  further comprising a second object transfer station that is situated adjacent to said polishing pad, said second object transfer station providing a place to transfer said objects from said object carriers after said objects have been polished.  
     
     
         10 . The apparatus of  claim 9  wherein said second object transfer station includes a thickness detection device to measure the thickness of said objects after said objects have been polished.  
     
     
         11 . The apparatus of  claim 1  wherein said polishing pad is a rotatable polishing pad, and wherein said object carriers are configured to be selectively separated from said carrier transfer assembly, said object carriers being transferred to said different positions by said rotatable polishing pad when said object carriers are separated from said carrier transfer assembly and placed on said polishing pad.  
     
     
         12 . The apparatus of  claim 11  further comprising an aligning device that is positioned adjacent to said polishing pad such that said aligning device can contact one of said object carriers to align that object carrier to a desired position of said different positions.  
     
     
         13 . The apparatus of  claim 1  further comprising a pad conditioner connected to a curved arm, said curved arm being pivotable about an axis such that said pad conditioner sweeps said polishing pad when said curved arm is pivoted.  
     
     
         14 . The apparatus of  claim 1  wherein said polishing pad is configured to be rotated about a rotational axis, and wherein said carrier transfer assembly is configured to rotate said object carriers about a central axis to transfer said object carriers to said different positions.  
     
     
         15 . The apparatus of  claim 14  wherein said polishing pad and said carrier transfer assembly are situated such that said rotational axis is aligned with said central axis.  
     
     
         16 . The apparatus of  claim 14  wherein said polishing pad and said carrier transfer assembly are situated such that said rotational axis is not aligned with said central axis.  
     
     
         17 . The apparatus of  claim 1  wherein said polishing pad is configured to be rotated about a rotational axis that differs from an axis that intersects the center of said polishing pad.  
     
     
         18 . The apparatus of  claim 1  wherein said polishing pad is a polishing belt having a predefined width, said polishing belt being configured to be moved in a direction substantially perpendicular to said predefined width.  
     
     
         19 . The apparatus of  claim 18  wherein said predefined width of said polishing belt is sufficiently wide to accommodate said object carriers such that all of said object carriers can be placed on a polishing surface of said polishing belt.  
     
     
         20 . The apparatus of  claim 18  wherein said different positions are misaligned on said polishing pad with respect to said direction of said polishing pad.  
     
     
         21 . The apparatus of  claim 1  wherein said carrier transfer assembly is configured to radially move each of said object carriers independently.  
     
     
         22 . The apparatus of  claim 1  wherein said carrier transfer assembly is configured to move each of said object carriers independently in a lateral direction, said lateral direction being substantially perpendicular to a radial direction of said polishing pad.  
     
     
         23 . An apparatus for polishing surfaces of objects comprising: 
 a polishing belt of a predefined width having a polishing surface;    a plurality of object carriers, said object carriers being configured to secure said objects to be polished; and    a carrier transfer assembly that is configured to sequentially transfer each of said object carriers to different positions on said polishing belt to polish said objects on said polishing surface of said polishing belt.    
     
     
         24 . The apparatus of  claim 23  further comprising a first object transport device that sequentially transports said objects to said object carriers when said object carriers are transferred to a first location that is associated with a first position of said different positions.  
     
     
         25 . The apparatus of  claim 24  wherein said first object transport device is configured to sequentially transport said objects from said object carriers when said object carriers are situated at said first location.  
     
     
         26 . The apparatus of  claim 24  wherein said first location laterally coincides with said first position of said different positions on said polishing belt.  
     
     
         27 . The apparatus of  claim 24  further comprising a second object transport device that sequentially transports said objects from said object carriers when said object carriers are transferred to a second location that is associated with a second position of said different positions.  
     
     
         28 . The apparatus of  claim 27  wherein said second location laterally coincides with said second position of said different positions on said polishing belt.  
     
     
         29 . The apparatus of  claim 23  further comprising a first object transfer station that is situated adjacent to said polishing belt to transfer said objects to said object carriers for polishing.  
     
     
         30 . The apparatus of  claim 29  wherein said object transfer station includes a thickness detection device to measure the thickness of said objects.  
     
     
         31 . The apparatus of  claim 29  further comprising a second object transfer station that is situated adjacent to said polishing belt, said second object transfer station providing a place to transfer said objects from said object carriers after said objects have been polished.  
     
     
         32 . The apparatus of  claim 31  wherein said object transfer station includes a thickness detection device to measure the thickness of said objects after said objects have been polished.  
     
     
         33 . The apparatus of  claim 23  wherein said predefined width of said polishing belt is sufficiently wide to accommodate said object carriers such that all of said object carriers can be placed on said polishing surface of said polishing belt.  
     
     
         34 . The apparatus of  claim 23  further comprising a rotatable polishing pad that is situated adjacent to said polishing belt, and wherein said carrier transfer assembly is further configured to sequentially transfer said object carriers to said rotatable polishing pad.  
     
     
         35 . The apparatus of  claim 23  wherein said different positions are misaligned with respect to said direction of said polishing pad.  
     
     
         36 . The apparatus of  claim 23  wherein said carrier transfer assembly is configured to radially move each of said object carriers independently.  
     
     
         37 . The apparatus of  claim 23  wherein said carrier transfer assembly is configured to move each of said object carriers independently in a lateral direction, said lateral direction being substantially perpendicular to a radial direction of said polishing pad.  
     
     
         38 . An apparatus for polishing surfaces of objects comprising: 
 a polishing pad having a polishing surface;    a plurality of object carriers, said object carriers being configured to secure said objects to be polished; and    a plurality of carrier shafts that are configured to be attached to said object carriers, said carrier shafts and said object carriers being further configured to be selectively separated such that said object carriers when separated can be transferred to different positions on said polishing pad by the rotation of said polishing pad.    
     
     
         39 . The apparatus of  claim 38  further comprising an aligning device that is positioned on the periphery of said polishing pad such that said aligning device can contact one of said object carriers to align that object to a desired position of said different positions.  
     
     
         40 . The apparatus of  claim 38  further comprising a plurality of carrier mechanisms coupled to said carrier shafts, said carrier mechanisms being configured to radially move each of said object carriers independently when said object carriers are attached to said carrier shafts.  
     
     
         41 . A method of polishing surfaces of objects comprising: 
 loading a first object onto a first object carrier;    transferring said first object carrier to a first polishing position on a polishing pad;    polishing said first object at said first polishing position;    loading a second object onto a second object carrier while said first object is approximately positioned at said first polishing position; and    transferring said first object carrier and said second object carriers to different polishing positions on said polishing pad such that said first and second objects are exclusively polished on said polishing pad.    
     
     
         42 . The method of  claim 41  wherein said step of loading said first object onto said first object carrier includes loading said first object onto said first object carrier situated at an object-transport location that coincides with one of said different polishing positions.  
     
     
         43 . The method of  claim 42  further comprising a step of polishing a prior object secured on said first object carrier at said object transport location, said step of polishing said prior object and said step of loading said first object onto said first object carrier being executed without transferring said first object carrier to a different polishing position.  
     
     
         44 . The method of  claim 43  further comprising a step of unloading said first object from said first object carrier when said first object carrier is transferred back to said object-transport location.  
     
     
         45 . The method of  claim 42  further comprising a step of unloading a polished object from said first object carrier at a second object-transport location that is associated with a second polishing position of said different polishing positions.  
     
     
         46 . The method of  claim 41  wherein said step of transferring said first object carrier and said second object carrier includes rotating said polishing pad about a rotational axis with said first object carrier and said second object carrier on said polishing pad to transfer said first and second object carriers to said different polishing positions on said polishing pad.  
     
     
         47 . The method of  claim 46  further comprising a step of extending a stopping device into a rotational path of said first object carrier and said second object carrier on said polishing pad to align said first object carrier and said second object carrier at specified positions of said different polishing positions.  
     
     
         48 . The method of  claim 41  further comprising a step of conditioning said polishing pad with a pad conditioner on a curved arm, said curved arm being pivotable about an axis to sweep said polishing surface of said polishing pad with said pad conditioner.  
     
     
         49 . The method of  claim 41  wherein said step of transferring said first object carrier and said second object carrier includes rotating said first object carrier and said second object carrier about a central axis, said central axis being aligned to a rotational axis of said polishing pad.  
     
     
         50 . The method of  claim 41  wherein said step of transferring said first carrier and said second object carrier includes rotating said first object carrier and said second object carrier about a central axis, said central axis being not aligned to a rotational axis of said polishing pad.  
     
     
         51 . The method of  claim 41  wherein said step of polishing said first object include rotating said polishing pad about a rotational axis that differs from an axis that intersects the center of said polishing pad.  
     
     
         52 . The method of  claim 41  wherein said step of polishing said first object includes moving said polishing pad in a linear direction.  
     
     
         53 . The method of  claim 41  further comprising a step of measuring the thickness of said first object before and after said first object is polished.  
     
     
         54 . The method of  claim 53  further comprising a step of adjusting polishing parameters in response to said step of measuring the thickness of said first object.  
     
     
         55 . The method of  claim 41  further comprising a step of polishing said first object as said first object carrier is transferred to said different polishing positions.  
     
     
         56 . The method of  claim 41  further comprising a step of radially moving each of said first object carrier and said second object carrier independently.  
     
     
         57 . The method of  claim 41  further comprising a step of moving each of said first object carrier and said second object carrier independently in a lateral direction, said lateral direction being substantially perpendicular to a radial direction of said polishing pad.