Front-reference carrier on orbital solid platen

Abstract

The present invention is an apparatus and method for planarizing a front surface of a wafer. The present invention may include a rigid platen, for supporting a polishing pad, connected to a supporting base that has means, or is connected to means, for orbiting the platen. A carrier, preferably a front-reference carrier with a plurality of individually controllable pressure areas, may be used to hold and press the wafer against the polishing pad while the supporting base orbits the rigid platen. The planarization process may be further optimized by orbiting the polishing pad in a radius smaller than 4 mm, orbiting the polishing pad faster than 400 orbits per minute or both.

We claim:  
     
         1 . An apparatus for planarizing a wafer comprising: 
 a) a rigid platen;    b) a supporting base connected to the platen for moving the platen in an orbital motion;    c) a polishing pad mounted on the platen; and    d) a carrier adapted for holding and pressing a wafer against the polishing pad.    
     
     
         2 . The apparatus of  claim 1  further comprising: 
 a) a shaft connected to the carrier; and  
 b) a motor connected to the shaft adapted for rotating the shaft and the carrier.  
 
     
     
         3 . The apparatus of  claim 1  wherein the carrier is a front-reference carrier.  
     
     
         4 . The apparatus of  claim 1  wherein the carrier is a back-reference carrier.  
     
     
         5 . The apparatus of  claim 3  wherein the carrier may be adjusted to provide a plurality of individually controllable pressure areas on the back surface of the wafer.  
     
     
         6 . The apparatus of  claim 1  wherein the supporting base is adapted to orbit the polishing pad at an orbital radius of less than about four mm.  
     
     
         7 . The apparatus of  claim 1  wherein the supporting base is adapted to orbit the polishing pad at an orbital rate faster than about 400 orbits per minute.  
     
     
         8 . A method of planarizing a wafer comprising the steps of: 
 a) loading a wafer into a carrier;    b) positioning the wafer adjacent a polishing pad mounted to a solid platen;    c) pressing the wafer against the polishing pad;    d) orbiting the polishing pad; and    e) removing the wafer from the polishing pad.    
     
     
         9 . The method of  claim 8  further comprising the step of: 
 a) rotating the wafer prior to removing the wafer from the polishing pad.  
 
     
     
         10 . The method of  claim 8  further comprising the step of: 
 a) alternately rotating the wafer in a clock-wise direction and a counterclockwise direction prior to removing the wafer from the polishing pad.  
 
     
     
         11 . The method of  claim 8  wherein the pressing step further comprises the steps of: 
 applying a first pressure against a central area on a back surface of the wafer; and  
 applying a second pressure against a concentric peripheral area in relation to the central region, wherein the second pressure is different than the first pressure.  
 
     
     
         12 . The method of  claim 8  wherein the polishing pad is orbited faster than about 400 orbits per minute.  
     
     
         13 . The method of  claim 8  wherein the polishing pad is orbited in a radius smaller than about four mm.  
     
     
         14 . The method of  claim 8  wherein the polishing pad is orbited faster than about 400 orbits per minute in an orbital radius smaller than about four mm.  
     
     
         15 . The method of  claim 8  wherein the carrier is a front-reference carrier.