Apparatus and method of detecting endpoint of a dielectric etch

Abstract

A system detects the clearing of a dielectric at a plurality of contact sites by measuring the surface voltage of the dielectric and comparing the surface voltage to a reference voltage set to a value that relates to the cleared contact sites. Another system detects the clearing of a dielectric at a plurality of contact sites on a substrate by measuring the rate of change of a substrate current during an etch process and ending the etch process when the rate of change is approximately zero. Another system detects the clearing of a dielectric at a contact site by measuring a substrate current during an etch process and ends the etch process when the measured substrate current exceeds a predetermined value.

1 . A method comprising: 
 placing a substrate in a plasma etch chamber;    etching the substrate;    measuring a substrate current; and    stopping the etching when the substrate current stabilizes.    
   
   
       2 . The method of  claim 1 , wherein etching the substrate includes inducing a substrate current with plasma ions.  
   
   
       3 . A method comprising: 
 placing a substrate in a plasma etch chamber;    etching the substrate;    measuring a substrate current having a rate of change;    stopping the etching when the rate of change of the substrate current is substantially zero.    
   
   
       4 . The method of  claim 3 , wherein etching the substrate includes inducing a substrate current with plasma ions.  
   
   
       5 . The method of  claim 3 , wherein measuring a substrate current includes measuring the substrate current in real time while the substrate is etched.  
   
   
       6 . A method comprising: 
 placing a substrate having a layer to etch in a plasma etch chamber;    etching the layer;    measuring a substrate current; and    stopping the etching when the substrate current stabilizes.    
   
   
       7 . The method of  claim 6 , wherein measuring a substrate current includes measuring the substrate current in real time while the layer is etched.  
   
   
       8 . The method of  claim 6 , wherein placing the substrate includes placing a substrate having a dielectric layer including one of an oxide, a nitride, borophosphosilicate, silicon-dioxides, silicon-nitrides, and tetra-ethyl-ortho-silicates.  
   
   
       9 . A method comprising: 
 placing a substrate having a layer to etch in a plasma etch chamber;    etching the layer;    measuring a rate of change of a substrate current; and    stopping the etching when the rate of change of the substrate current is approximately zero.    
   
   
       10 . The method of  claim 9 , wherein etching the layer includes inducing a substrate current with plasma ions.  
   
   
       11 . The method of  claim 9 , wherein measuring the rate of change of a substrate current includes measuring a substrate current in real time while the layer is etched.  
   
   
       12 . A method comprising: 
 placing a substrate having a layer to etch in a plasma etch chamber;    etching the layer;    measuring a substrate current; and    stopping the etching when the substrate current exceeds a predetermined reference value.    
   
   
       13 . The method of  claim 12 , wherein stopping the etching when the substrate current exceeds a predetermined reference value includes setting the reference current to a value approximately equal to a substrate current when contacts formed in the layer are cleared of dielectric.  
   
   
       14 . The method of  claim 13 , wherein setting the reference current includes determining the reference substrate current for a given manufacturing step, wherein determining the reference substrate current includes: 
 measuring the substrate current at an end of a manufacturing step; and    verifying that the contacts are cleared of dielectric.    
   
   
       15 . The method of  claim 13 , wherein setting the reference current includes selecting the reference current from a range of current values related to the etching process parameters.  
   
   
       16 . A method comprising: 
 placing a substrate having a dielectric layer to etch in a plasma etch chamber;    etching the dielectric layer;    measuring a substrate current; and    stopping the etching when the substrate current stabilizes.    
   
   
       17 . A method comprising: 
 placing a substrate having a dielectric layer to etch in a plasma etch chamber;    etching the dielectric layer;    measuring a rate of change of a substrate current; and    stopping the etching when the rate of change of the substrate current is substantially zero.    
   
   
       18 . The method of  claim 17 , wherein etching the substrate includes inducing a substrate current with plasma ions.  
   
   
       19 . The method of  claim 18 , wherein measuring a rate of change of a substrate current includes measuring the current in real time while the dielectric layer is being etched.  
   
   
       20 . A method comprising: 
 placing a substrate having a dielectric layer to etch in a plasma etch chamber;    etching the dielectric layer;    measuring a substrate current; and    stopping the etching process when the substrate current exceeds a predetermined reference value.    
   
   
       21 . The method of  claim 20 , wherein etching the dielectric layer includes forming contacts.  
   
   
       22 . The method of  claim 21 , wherein stopping the etching process when the substrate current exceeds a predetermined reference value includes setting the reference current to a value approximately equal to a substrate current when the contacts are cleared of dielectric.  
   
   
       23 . The method of  claim 22 , wherein setting the reference current to a value includes selecting the value from a range of current values related to the etching process parameters.  
   
   
       24 . The method of  claim 22 , wherein setting the reference current includes determining the reference substrate current for a given manufacturing step, wherein determining the reference substrate current includes: 
 measuring the substrate current at an end of a manufacturing step; and    verifying that the contacts are cleared of dielectric.    
   
   
       25 . A method for etching a dielectric on a substrate, comprising: 
 placing the substrate having a dielectric to etch within an etching chamber;    setting a reference current to a value related to a substrate current when a contact is cleared of the dielectric;    etching the dielectric in the etching chamber;    measuring the current in the substrate;    generating an endpoint detection signal when the measured current is greater than the reference current;    detecting the endpoint detection signal; and    stopping the etching when the endpoint detection signal is detected.    
   
   
       26 . The method of  claim 25 , wherein setting the reference current includes setting the reference current to a value approximately equal to the substrate current when the contact is cleared of dielectric.  
   
   
       27 . The method of  claim 25 , wherein setting the reference current includes determining the reference substrate current for a given manufacturing step, wherein determining the reference substrate current includes: 
 measuring the substrate current at an end of a manufacturing step; and    verifying that the contact is cleared of dielectric.    
   
   
       28 . The method of  claim 25 , wherein the reference current is selectable from a range of current values related to the etching process parameters.  
   
   
       29 . The method of  claim 25 , wherein placing the substrate includes placing a semiconductor substrate.  
   
   
       30 . The method of  claim 25 , wherein detecting the endpoint detection signal includes visually detecting the endpoint detection signal.  
   
   
       31 . The method of  claim 25 , wherein detecting the endpoint detection signal includes detecting a digital output signal.  
   
   
       32 . The method of  claim 25 , wherein detecting the endpoint detection signal includes detecting an analog signal.  
   
   
       33 . A method comprising: 
 placing a substrate having a dielectric layer to etch in an etching chamber;    etching the dielectric layer;    measuring a substrate current in real time while the layer is etched; and    stopping the etching process when the substrate current exceeds a predetermined reference value.    
   
   
       34 . The method of  claim 33 , wherein etching the dielectric layer includes a substrate current increasing during the etching.