Control of polishing of multiple substrates on the same platen in chemical mechanical polishing

Abstract

A polishing method includes positioning two substrates in contact with the same polishing pad. Prior to commencement of polishing and while the two substrates are in contact with the polishing pad, two starting values are generated from an in-situ monitoring system. Either a starting polishing time or a pressure applied to one of the substrates can be adjusted so that the two substrates have closer endpoint conditions. During polishing the two substrates are monitored with the in-situ monitoring system to generate a two sequences of values, and a polishing endpoint can be detected or an adjustment for a polishing parameter can be based on the two sequences of values.

What is claimed is: 
     
         1 . A polishing method, comprising:
 positioning a first substrate and a second substrate in contact with the same polishing pad;   prior to commencement of polishing and while the first substrate and second substrate are in contact with the polishing pad, generating from an in-situ monitoring system a first starting value and a second starting value from the first substrate and the second substrate, respectively;   calculating an adjusted first pressure for the first substrate;   polishing the first substrate on the polishing pad with the adjusted pressure and polishing the second substrate on the polishing pad with a second pressure;   monitoring the first substrate and the second substrate during polishing with the in-situ monitoring system to generate a first sequence of values for the first substrate and a second sequence of values for the second substrate; and   at least one of detecting a polishing endpoint for the first substrate and the second substrate or determining an adjustment for a polishing parameter based on the first sequence of values and the second sequence of values.   
     
     
         2 . The method of  claim 1 , wherein calculating the adjusted first pressure comprises a default pressure multiplied by a ratio based on the first starting value and the second starting value. 
     
     
         3 . The method of  claim 2 , wherein the default pressure is a preset pressure or a pressure dynamically calculated based on monitoring of a prior substrate. 
     
     
         4 . The method of  claim 2 , wherein calculating the adjusted first pressure P ADJ1  comprises calculating P ADJ1 =P DEF1 *(TV−V2)/(TV−V1), where TV is a target value, V1 is the first starting value, V2 is the second starting value, and P DEF1  is the default pressure. 
     
     
         5 . The method of  claim 4 , comprising detecting the polishing endpoint. 
     
     
         6 . The method of  claim 5 , wherein detecting the polishing endpoint comprises fitting a first function to the first sequence of values and determining a time at which the first function equals the target value, or fitting a second function to the second sequence of values and determining a time at which the second function equals the target value. 
     
     
         7 . The method of  claim 1 , wherein the in-situ monitoring system comprises an eddy current monitoring system, and wherein polishing the first substrate comprises polishing a first metal layer on the first substrate and polishing the second substrate comprises polishing a second metal layer on the second substrate. 
     
     
         8 . The method of  claim 1 , wherein the in-situ monitoring system comprises a spectrographic monitoring system, and wherein polishing the first substrate comprises polishing a first dielectric layer on the first substrate and polishing the second substrate comprises polishing a second dielectric layer on the second substrate. 
     
     
         9 . The method of  claim 1 , wherein the first substrate is the substrate having a thicker layer to be polished. 
     
     
         10 . The method of  claim 1 , wherein the first substrate is the substrate having a thinner layer to be polished. 
     
     
         11 . A polishing method, comprising:
 positioning a first substrate and a second substrate in contact with the same polishing pad;   prior to commencement of polishing and while the first substrate and second substrate are in contact with the polishing pad, generating from an in-situ monitoring system a first starting value and a second starting value from the first substrate and the second substrate, respectively;   calculating a delay time for the second substrate based on the first starting value and the second starting value;   polishing the first substrate on the polishing pad;   after the delay time from commencing polishing of the first substrate, polishing the second substrate on the polishing pad;   monitoring the first substrate and the second substrate during polishing with the in-situ monitoring system to generate a first sequence of values for the first substrate and a second sequence of values for the second substrate; and   at least one of detecting a polishing endpoint for the first substrate and the second substrate or determining an adjustment for a polishing parameter based on the first sequence of values and the second sequence of values.   
     
     
         12 . The method of  claim 11 , wherein calculating the delay time comprises a difference between the first starting value and the second starting value divided by a default polishing rate. 
     
     
         13 . The method of  claim 12 , wherein the default polishing rate is a preset polishing rate or a polishing rate dynamically calculated based on monitoring of a prior substrate. 
     
     
         14 . The method of  claim 12 , wherein calculating the delay time comprises calculating ΔT=(V2−V1)/R, where V1 is the first starting value, V2 is the second starting value, and R is the default polishing rate. 
     
     
         15 . The method of  claim 14 , comprising detecting the polishing endpoint. 
     
     
         16 . The method of  claim 15 , wherein detecting the polishing endpoint comprises fitting a first function to the first sequence of values and determining a time at which the first function equals the target value, or fitting a second function to the second sequence of values and determining a time at which the second function equals a target value. 
     
     
         17 . The method of  claim 11 , wherein the in-situ monitoring system comprises an eddy current monitoring system, and wherein polishing the first substrate comprises polishing a first metal layer on the first substrate and polishing the second substrate comprises polishing a second metal layer on the second substrate. 
     
     
         18 . The method of  claim 11 , wherein the in-situ monitoring system comprises an spectrographic monitoring system, and wherein polishing the first substrate comprises polishing a first dielectric layer on the first substrate and polishing the second substrate comprises polishing a second dielectric layer on the second substrate. 
     
     
         19 . The method of  claim 1 , wherein the second substrate is the substrate having a thinner layer to be polished.