Method and apparatus for endpointing mechanical and chemical-mechanical polishing of substrates

Abstract

An apparatus and method for stopping mechanical and chemical-mechanical polishing of a substrate at a desired endpoint. In one embodiment, a polishing machine has a platen, a polishing pad positioned on the platen, and a polishing medium located at a planarizing surface of the polishing pad. The polishing machine also has a substrate carrier that may be positioned over the planarizing surface of the polishing pad, and at least one heat sensor is coupled to the polishing machine to detect heat at a front side of the substrate. The heat sensor preferably measures a temperature of a component sensitive to heat at the front side of the substrate, such as the planarizing surface of the polishing pad, the back side of the substrate, or the byproducts produced by polishing the substrate. In operation, the heat sensor monitors the heat at the front side of the substrate, and the removal of material from the substrate is stopped when the heat at the front side of the substrate changes from a first heat range to a second heat range.

1. A method for stopping polishing of a substrate at a desired endpoint, the substrate having a cover layer and an underlying layer under the cover layer, the method comprising:
 monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the component comprises byproducts produced by polishing the substrate and the characteristic is a temperature of the byproducts, and wherein the monitoring step comprises sensing the temperature of the byproducts; and  
 stopping removal of material from the substrate when the characteristic of the polishing component is at a predetermined value that indicates the material being removed from the planarized surface is at the desired endpoint of the substrate.  
 
     
     
       2. The method of  claim 1  wherein the sensing step comprises measuring a temperature of a planarizing liquid flowing off of a polishing pad. 
     
     
       3. A method for stopping mechanical and chemical-mechaniical polishing of a substrate at an endpoint, the substrate having a cover layer and an underlying layer under the cover layer, and the method comprising:
 monitoring heat transfer at a planarized surface of the substrate and a polishing component sensitive to heat at the planarized surface by measuring a temperature of the component, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping polishing of the substrate when the characteristic of the polishing component is at a predetermined value that indicates the planarized surface is at the desired endpoint.  
 
     
     
       4. The method of  claim 3  wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad. 
     
     
       5. A method for stopping mechanical and chemical-mechanical polishing of a substrate at an endpoint, the method comprising:
 detecting a change in heat at a front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages a polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting a change in heat at the front side of the substrate comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping removal of material from the substrate when the heat is a predetermined value that indicates a desired portion of the underlying layer is exposed at the front side of the substrate.  
 
     
     
       6. The method of  claim 5  wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad. 
     
     
       7. A method of stopping mechanical and chemical-mechanical polishing of a substrate at an endpoint, the method comprising:
 measuring a temperature of a component sensitive to heat at a front side of the substrate, the component temperature being different when a cover layer of the substrate engages a polishing medium than when a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping removal of material from the substrate when the component temperature changes from the first temperature to the second temperature range.  
 
     
     
       8. A method of polishing a substrate, comprising:
 removing material from a front side of the substrate with a polishing medium, the polishing medium being positioned at a planarizing surface of a polishing pad;  
 monitoring heat at the front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages the polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein monitoring the heat comprises measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being a first temperature when the cover layer of the substrate engages the polishing medium and the component temperature being a second temperature when at least a portion of the underlying layer of the substrate engages the polishing medium, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping removal of material from the substrate when the heat at the front side of the substrate is a predetermined value that indicates a desired portion of the cover layer has been removed from the substrate.  
 
     
     
       9. The method of  claim 8  wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad. 
     
     
       10. A method of polishing a substrate, comprising:
 removing material from a front side of the substrate with a polishing medium, the polishing medium being positioned at a planarizing surface of a polishing pad;  
 detecting a change in heat at the front side of the substrate, the heat at the front side of the substrate being in a first range when a cover layer of the substrate engages the polishing medium and the heat being in a second range when a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting the change in heat comprises measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being in a first temperature range when the heat at the front side of the substrate is in the first heat range and the component temperature being in a second temperature range when the heat at the front side of the substrate is in the second heat range, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping removal of material from the substrate when the heat at the front side of the substrate is in the second range.  
 
     
     
       11. The method of  claim 10  wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad. 
     
     
       12. A method of polishing a substrate, comprising:
 removing material from a front side of the substrate with a polishing medium, the polishing medium being positioned at a planarizing surface of a polishing pad;  
 measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being different when a cover layer of the substrate engages the polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and  
 stopping removal of material from the substrate when the component temperature changes from the first temperature range to the second temperature range.  
 
     
     
       13. The method of  claim 12  wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polished pad. 
     
     
       14. A method for stopping polishing of a substrate at a desired endpoint, comprising:
   monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the polishing component comprises byproducts produced by polishing the substrate and the characteristic is an emission spectrum of the byproducts, and wherein monitoring a characteristic comprises analyzing the emission spectrum; and        stopping removal of material from the substrate when the characteristic of the polishing component that is monitored indicates the material being removed from the planarized surface is at the desired endpoint of the substrate.     
     
     
       15. A method for determining when the polishing of a substrate has reached an endpoint, the substrate having a cover layer and an underlying layer under the cover layer, the method comprising monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the component comprises byproducts produced by polishing the substrate and the characteristic is a temperature of the byproducts, and wherein the monitoring step comprises sensing the temperature of the byproducts. 
     
     
       16. A method for determining when the polishing of a substrate has reached an endpoint, the method comprising detecting a change in heat at a front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages a polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting a change in heat at the front side of the substrate comprises sensing a temperature of byproducts by polishing the substrate. 
     
     
       17. The method of  claim 16  wherein the temperature sensing act comprises measuring a temperature of a planarizing solution flowing off of the polishing pad. 
     
     
       18. The method of  claim 14  wherein the emission spectrum is characteristic of a temperature of the byproducts. 
     
     
       19. The method of  claim 14  wherein the emission spectrum is characteristic of a temperature of the byproducts and wherein analyzing the emission spectrum comprises sensing the temperature with an optical temperature sensor.