In-situ pad and wafer cleaning during chemical mechanical polishing

Abstract

A method for in-situ cleaning a polishing pad and a wafer surface simultaneously during copper chemical mechanical polishing and an apparatus for carrying out such method are disclosed. The method is carried out by dispensing an acid-containing solution onto a top surface of a polishing pad while the wafer is rotated against the polishing pad without any slurry solution being dispensed. The acid-containing solution may be advantageously formed by diluting an acid such as citric acid, HCOOH, CH 3 COOH, HNO 3 , H 2 SO 4 and HF to a concentration of less than 10 wt. % acid, preferably less than 5 wt. % acid, and more preferably less than 1 wt. % acid. The acid-containing solution may be dispensed onto a top surface of the polishing pad for a time period between about 30 sec. and about 300 sec.

What is claimed is:  
     
         1 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing comprising the steps of: 
 rotating a wafer and a polishing pad in opposite directions;    conducting a chemical mechanical polishing process on a wafer surface;    stopping the dispensing of a slurry solution onto a top surface of said polishing pad; and    dispensing an acid-containing solution onto said top surface of said polishing pad while said wafer and said pad are being rotated.    
     
     
         2 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of mixing said acid-containing solution from water and an acid selected from the group consisting of citric acid, HCOOH, CH 3 COOH, HNO 3 , H 2 SO 4  and HF.  
     
     
         3 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of mixing said acid-containing solution to a concentration of not higher than 10 wt. % acid.  
     
     
         4 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of dispensing said acid-containing solution for a time period of at least 30 sec.  
     
     
         5 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of dispensing said acid-containing solution for a time period of between about 30 sec. and about 300 sec.  
     
     
         6 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of dispensing said acid-containing solution to a concentration of preferably not higher than 5 wt. % acid.  
     
     
         7 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of dispensing said acid-containing solution to a concentration of more preferably not higher than 1 wt. % acid.  
     
     
         8 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of mixing said acid-containing solution by 0.4 wt. % citric acid and 99.5 wt. % water.  
     
     
         9 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of removing Cu x O from said pad and said wafer by said acid-containing solution.  
     
     
         10 . A method for in-situ cleaning a pad and a wafer during chemical mechanical polishing according to  claim 1  further comprising the step of dispensing said acid-containing solution while said wafer and said pad are rotated in opposite directions at a rotational speed of at least 50 rpm.  
     
     
         11 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head comprising: 
 a wafer carrier for holding a wafer therein and for rotating the wafer at a first rotational direction;    a polishing platen for holding a polishing pad thereon and for rotating the pad at a second rotational direction opposite to said first rotational direction;    a slurry dispensing arm for dispensing a slurry solution from a dispensing nozzle onto a top surface of the polishing pad; and    a cleaning solution dispensing arm for dispensing an acid-containing solution from a dispensing nozzle onto said top surface of the polishing pad.    
     
     
         12 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11  further comprising metering means for metering components for said acid-containing solution.  
     
     
         13 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11 , wherein said cleaning solution dispensing arm further comprises at least one dispensing nozzle for dispensing said acid-containing solution.  
     
     
         14 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11 , wherein said cleaning solution dispensing arm further comprises a plurality of dispensing nozzles for dispensing said acid-containing solution substantially over the entire surface of said polishing pad.  
     
     
         15 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 12  further comprising mixing means for mixing said components that are metered by said metering means for making said acid-containing solution.  
     
     
         16 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11  further comprising a pad conditioning arm and a pad conditioning disk for conditioning said polishing pad.  
     
     
         17 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11 , wherein said cleaning solution dispensing arm being connected unitarily to said slurry dispensing arm for dispensing said acid-containing solution.  
     
     
         18 . A chemical mechanical polishing apparatus incorporating an in-situ pad and wafer cleaning head according to  claim 11  further comprising an interlock means for dispensing said acid-containing solution only when said dispensing of the slurry solution is stopped.