Chemical mechanical polishing using fluorescence-based endpoint detection

Abstract

A polishing tool and methodology are disclosed, particularly useful for chemical mechanical polish (CMP) applications (e.g., polishing and planarizing). In an embodiment, the tool includes a carrier structure configured to support a workpiece, a polishing pad configured to rotate and polish at least a portion of the workpiece, a source configured to generate excitation radiation directed towards the workpiece, and a detector configured to receive fluorescence radiation from the workpiece. The fluorescence radiation is generated by absorption of the excitation radiation by a polymer material on the workpiece. The polishing tool also includes a controller configured to, based on a magnitude of the received fluorescence radiation, change at least one operating condition of the polishing tool. For instance, the controller can speed or slow the polishing process, and stop the polishing process when a target thickness is achieved.

What is claimed is: 
     
         1 . A polishing tool, comprising:
 a carrier structure configured to support a workpiece;   a polishing pad configured to rotate and polish at least a portion of the workpiece;   a source configured to generate excitation radiation directed towards the workpiece;   a detector configured to receive fluorescence radiation from the workpiece, the fluorescence radiation generated by absorption of the excitation radiation; and   a controller configured to, based on a magnitude of the received fluorescence radiation, change at least one operating condition of the polishing tool.   
     
     
         2 . The polishing tool of  claim 1 , wherein the source comprises an ultraviolet (UV) source. 
     
     
         3 . The polishing tool of  claim 1 , further comprising a first optical fiber configured to direct the generated excitation radiation towards the workpiece, and a second optical fiber configured to collect fluorescence radiation from the workpiece and to direct the fluorescence radiation towards the detector. 
     
     
         4 . The polishing tool of  claim 1 , wherein the controller is configured to halt rotation of the polishing pad in response to the magnitude of the received fluorescence radiation falling below a threshold value. 
     
     
         5 . The polishing tool of  claim 1 , wherein the controller is configured to increase or decrease a rotation speed of the polishing pad based on the magnitude of the received fluorescence radiation. 
     
     
         6 . The polishing tool of  claim 1 , further comprising a memory configured to store data that associates given thicknesses of a polymer material with corresponding fluorescence magnitudes. 
     
     
         7 . The polishing tool of  claim 6 , wherein the controller is configured to compare the magnitude of the received fluorescence radiation to the stored data having corresponding fluorescence magnitudes to determine a thickness of the polymer material present on the workpiece. 
     
     
         8 . A method of polishing a polymer material, the method comprising:
 bringing the polymer material, via a carrier structure, into contact with a polishing pad;   rotating the polishing pad to polish the polymer material;   directing excitation radiation towards the polymer material;   receiving fluorescence radiation from the polymer material, the fluorescence radiation generated from absorption of the excitation radiation; and   adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the received fluorescence radiation.   
     
     
         9 . The method of  claim 8 , wherein the polymer material comprises a polymer film that encapsulates at least a portion of a semiconductor die. 
     
     
         10 . The method of  claim 8 , wherein directing excitation radiation comprises directing UV radiation towards the polymer material. 
     
     
         11 . The method of  claim 8 , wherein directing excitation radiation comprises directing excitation radiation via a first optical fiber towards the polymer material, and wherein receiving fluorescence radiation comprises receiving fluorescence radiation via a second optical fiber from the polymer material. 
     
     
         12 . The method of  claim 8 , wherein the adjusting comprises halting rotation of the polishing pad. 
     
     
         13 . The method of  claim 8 , further comprising:
 accessing stored data from a memory, the stored data including thicknesses of the polymer material with corresponding fluorescence magnitudes; and   comparing the magnitude of the received fluorescence radiation to the corresponding fluorescence magnitudes in the stored data.   
     
     
         14 . A chemical mechanical process apparatus configured to execute the method of  claim 8 . 
     
     
         15 . A computer program product including one or more non-transitory machine-readable mediums encoding instructions that when executed by one or more processors cause a process to be carried out for polishing a polymer material, the process comprising:
 actuating a carrier structure coupled to the polymer material, to bring the polymer material into contact with a polishing pad;   rotating the polishing pad to polish the polymer material;   receiving fluorescence data associated with fluorescence radiation from the polymer material; and   adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the fluorescence data.   
     
     
         16 . The computer program product of  claim 15 , wherein the adjusting comprises one or both of: halting rotation of the polishing pad; increasing a rotation speed of the polishing pad; and decreasing the rotation speed of the polishing pad. 
     
     
         17 . The computer program product of  claim 15 , wherein the adjusting comprises actuating the carrier structure to move the polymer material away from the polishing pad. 
     
     
         18 . The computer program product of  claim 15 , wherein the process further comprises:
 accessing stored data from a memory, the stored data having given thicknesses of the polymer material with corresponding fluorescence magnitudes; and   comparing the magnitude of the received fluorescence data to the corresponding fluorescence magnitudes in the stored data.   
     
     
         19 . The computer program product of  claim 18 , wherein the process further comprises determining a thickness of the polymer material based on the comparing. 
     
     
         20 . A chemical mechanical process apparatus including the computer program product of  claim 15 .