Method and apparatus for end-point detection

Abstract

An apparatus for detecting the end-point of an electropolishing process of a metal layer formed on a wafer includes an end-point detector. The end-point detector is disposed adjacent the nozzle used to electropolish the wafer. In one embodiment, the end-point detector is configured to measure the optical reflectivity of the portion of the wafer being electropolished.

1 . A method of monitoring the end-point of an electroplishing process of a metal layer formed on a wafer, comprising: 
 rotating and translating the wafer;    applying a stream of electrolyte to a first portion of the metal layer to electropolish the first portion, wherein the stream of electrolyte is applied using a nozzle;    obtaining a first measurement of the first portion before the stream of electrolyte is applied to the first portion, wherein the first measurement is obtained using a first sensor disposed adjacent to a first side of the nozzle; and    obtaining a second measurement of the first portion after the stream of electrolyte is applied to the first portion, wherein the second measurement is obtained using a second sensor disposed adjacent to a second side of the nozzle, wherein the first side is opposite the second side of the nozzle, and wherein the nozzle, the first sensor, and the second sensor remain stationary while the wafer is rotated and translated.    
   
   
       2 . The method of  claim 1 , further comprising: 
 determining an electropolishing rate in a single rotation of the wafer chuck based on the difference between the first and second measurements.    
   
   
       3 . The method of  claim 2 , further comprising: 
 adjusting the speed of rotation or translation of the wafer based on the electropolishing rate.    
   
   
       4 . The method of  claim 2 , further comprising: 
 adjusting polishing power applied to the stream of electrolyte based on the electropolishing rate.    
   
   
       5 . The method of  claim 1 , further comprising: 
 obtaining a third measurement of a second portion of the metal layer that was electropolished by the nozzle in a previous rotation of the wafer chuck, wherein the third measurement is obtained using a third sensor disposed adjacent to a third side of the nozzle; and    obtaining a fourth measurement of a third portion of the metal layer that will be electropolished by the nozzle in a subsequent rotation of the wafer chuck, wherein the fourth measurement is obtained using a fourth sensor disposed adjacent to a fourth side of the nozzle, wherein the third side is opposite the fourth side.    
   
   
       6 . The method of  claim 5 , further comprising: 
 determining an electropolishing rate of one electropolishing cycle based on the difference between the third and fourth measurements.    
   
   
       7 . The method of  claim 6 , further comprising: 
 adjusting the speed of rotation or translation of the wafer chuck based on the electropolishing rate of one electropolishing cycle.    
   
   
       8 . The method of  claim 7 , further comprising: 
 adjusting polishing power applied to the stream of electrolyte based on the electropolishing rate of one electropolishing cycle.    
   
   
       9 . The method of  claim 5 , further comprising: 
 obtaining a fifth measurement of the first portion while the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion, wherein the fifth measurement is obtained using a fifth sensor disposed within the nozzle.    
   
   
       10 . The method of  claim 1 , further comprising: 
 obtaining a fifth measurement of the first portion while the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion, wherein the fifth measurement is obtained using a fifth sensor disposed within the nozzle.    
   
   
       11 . An apparatus for monitoring the end-point of an electroplishing process of a metal layer formed on a wafer, comprising: 
 a wafer chuck configured to hold the wafer;    a drive mechanism connected to the wafer chuck, the drive mechanism configured to rotate and translate the wafer chuck;    a nozzle configured to electroplish the metal layer, 
 wherein the nozzle is configured to apply a stream of electrolyte;  
   a first sensor disposed adjacent to a first side of the nozzle, 
 wherein the first sensor is configured to obtain a first measurement of a first portion of the metal layer before the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion; and  
   a second sensor disposed adjacent to a second side of the nozzle, 
 wherein the first side is opposite the second side of the nozzle,  
 wherein the second sensor is configured to obtain a second measurement of the first portion after the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion, and  
 wherein the nozzle, the first sensor, and the second sensor are stationary.  
   
   
   
       12 . The apparatus of  claim 11 , wherein the difference between the first and second measurements is used to determine an electropolishing rate in a single rotation of the wafer chuck.  
   
   
       13 . The apparatus of  claim 12 , wherein the electropolishing rate is used to adjust polishing power applied to the stream of electrolyte or the speed of rotation or translation of the wafer chuck.  
   
   
       14 . The apparatus of  claim 11 , further comprising: 
 a third sensor disposed adjacent to a third side of the nozzle, wherein the third sensor is configured to obtain a third measurement of a second portion of the metal layer that was electropolished by the nozzle in a previous rotation of the wafer chuck; and    a fourth sensor disposed adjacent to a fourth side of the nozzle, wherein the third side is opposite the fourth side, and wherein the fourth sensor is configured to obtain a fourth measurement of a third portion of the metal layer that will be electropolished by the nozzle in a subsequent rotation of the wafer chuck.    
   
   
       15 . The apparatus of  claim 14 , wherein the difference between the third and fourth measurements is used to determine an electropolishing rate of one electropolishing cycle.  
   
   
       16 . The apparatus of  claim 15 , wherein the electropolishing rate of one electropolishing cycle is used to adjust polishing power applied to the stream of electrolyte or the speed of rotation or translation of the wafer chuck.  
   
   
       17 . The apparatus of  claim 14 , further comprising: 
 a fifth sensor disposed within the nozzle, the fifth sensor configured to obtain a fifth measurement of the first portion while the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion.    
   
   
       18 . The apparatus of  claim 11 , further comprising: 
 a fifth sensor disposed within the nozzle, the fifth sensor configured to obtain a fifth measurement of the first portion while the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion.    
   
   
       19 . An apparatus for monitoring the end-point of an electroplishing process of a metal layer formed on a wafer, comprising: 
 a wafer chuck configured to hold the wafer;    a drive mechanism connected to the wafer chuck, the drive mechanism configured to rotate and translate the wafer chuck;    a nozzle configured to electroplish the metal layer, 
 wherein the nozzle is configured to apply a stream of electrolyte;  
   a first sensor disposed adjacent to a first side of the nozzle, 
 wherein the first sensor is configured to obtain a first measurement of a first portion of the metal layer before the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion;  
   a second sensor disposed adjacent to a second side of the nozzle, wherein the first side is opposite the second side of the nozzle, and wherein the second sensor is configured to obtain a second measurement of the first portion after the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion; and    a third sensor disposed within the nozzle, the third sensor configured to obtain a third measurement of the first portion while the nozzle applies the stream of electrolyte onto the first portion to electropolish the first portion, wherein the nozzle, the first sensor, the second sensor, and the third sensor are stationary.    
   
   
       20 . The apparatus of  claim 19 , further comprising: 
 a fourth sensor disposed adjacent to a third side of the nozzle, wherein the fourth sensor is configured to obtain a third measurement of a second portion of the metal layer that was electropolished by the nozzle in a previous rotation of the wafer chuck; and    a fifth sensor disposed adjacent to a fourth side of the nozzle, wherein the fifth side is opposite the fourth side, and wherein the fifth sensor is configured to obtain a fourth measurement of a third portion of the metal layer that will be electropolished by the nozzle in a subsequent rotation of the wafer chuck.