System, method, and medium for an endpoint detection scheme for copper low-dielectric damascene structures for improved dielectric and copper loss

Abstract

A system, method and medium of detecting a transition interface between a first dielectric material and an adjacent second dielectric material in a semiconductor wafer during a chemical-mechanical polishing process includes impinging an incident light of a predetermined wavelength on the semiconductor wafer at a first time, detecting at least one first intensity of at least one first reflected light, impinging the incident light of the predetermined wavelength on the semiconductor wafer at a second time, detecting at least one second intensity of at least one second reflected light, and determining a difference between the at least one first intensity and the at least one second intensity. If the difference between the at least one first intensity and the at least one second intensity is above a predetermined threshold, the chemical-mechanical polishing process is terminated.

1 . A polishing system for detecting a transition interface between a first dielectric material and an adjacent second dielectric material in a semiconductor wafer during a polishing process, the system comprising: 
 a polishing tool that executes the polishing process, the polishing process being executed to remove a first dielectric material and expose a second dielectric material of the semiconductor wafer;    a light source that generates incident light of at least one predetermined wavelength upon a surface of the semiconductor wafer;    a detector that detects at least one reflected light intensity from the surface of the second dielectric material;    a data processor, in communication with the detector, that analyzes the reflected light intensity to determine and produce a signal when the transition interface between the first dielectric and the second dielectric has been detected.    
   
   
       2 . The system of  claim 1 , wherein the data processor halts the polishing process when the transition interface has been detected.  
   
   
       3 . The system of  claim 1 , further comprising a user input device, wherein the user input device enables a user to define at least one of a predetermined threshold, indicating when the transition interface between the first dielectric and the second dielectric has been reached, a rate of measurement at which a difference between at least one first reflected light intensity and at least one second reflected light intensity is determined, and a predetermined slope indicating when the transition interface between the first dielectric and the second dielectric has been reached.  
   
   
       4 . The system of  claim 1 , wherein the incident light is multi-wavelength light.  
   
   
       5 . The system of  claim 4 , further comprising detecting at least a first specific wavelength at the at least one first intensity indicating the presence of the first dielectric material, and detecting at least a second specific wavelength at the at least one second intensity, indicating the presence of the second dielectric material.  
   
   
       6 . The system of  claim 1 , wherein the first dielectric material is a DARC film layer, and the second dielectric material is a low-k film layer.  
   
   
       7 . The system of  claim 1 , wherein said incident light reflected from the semiconductor wafer is captured at predefined time intervals.  
   
   
       8 . The system of  claim 1 , wherein the incident light source is a coherent or substantially coherent light source.  
   
   
       9 . The system of  claim 8 , wherein the wavelength of the incident light source is about 400 nm.  
   
   
       10 . The system of  claim 1 , wherein the incident light comprises a plurality of wavelengths in the range of approximately 400 nm to 900 nm.  
   
   
       11 . The system of  claim 1 , wherein the polishing process is terminated when the transition interface has been detected.  
   
   
       12 . A method of detecting a transition interface between a first dielectric material and an adjacent second dielectric material on a semiconductor wafer during a polishing process, the method comprising: 
 initiating the polishing process, said polishing process being implemented to remove the first dielectric material and expose the second dielectric material of the semiconductor wafer;    impinging an incident light of at least one predetermined wavelength on the semiconductor wafer;    detecting at least one first intensity of said incident light reflected from the semiconductor wafer at a first time;    detecting at least one second intensity of said incident light reflected from the semiconductor wafer at a second time;    determining a difference between the at least one first intensity and the at least one second intensity; and    providing a signal when the difference between the at least one first intensity and the at least one second intensity is above a predetermined threshold, wherein the signal indicates that the transition interface has been detected.    
   
   
       13 . The method of  claim 12 , further comprising receiving a user input, wherein the user input defines the predetermined threshold.  
   
   
       14 . The method of  claim 12 , further comprising, when the transition interface has been detected, terminating the polishing process.  
   
   
       15 . The method of  claim 12 , further comprising plotting a graph of the at least one first intensity and the at least one second intensity as a function of time.  
   
   
       16 . The method of  claim 15 , wherein the difference between the at least one first intensity and the at least one second intensity is calculated by determining a slope of the graph.  
   
   
       17 . The method of  claim 16 , wherein the transition interface has been detected when the slope of the graph is within range of or substantially equal to a predetermined slope.  
   
   
       18 . The method of  claim 17 , further comprising, when the transition interface has been detected, terminating the polishing process.  
   
   
       19 . The method of  claim 12 , wherein at least one of the at least one predetermined wavelengths is 400 nm.  
   
   
       20 . The method of  claim 12 , wherein the incident light is multi-wavelength light.  
   
   
       21 . The method of  claim 20 , further comprising detecting at least a first specific wavelength at the at least one first intensity, indicating the presence of the first dielectric material, and detecting at least a second specific wavelength at the at least one second intensity, indicating the presence of the second dielectric material.  
   
   
       22 . The method of  claim 12 , wherein the first dielectric material is a DARC film layer, and the second dielectric material is a low-k film layer.  
   
   
       23 . The method of  claim 12 , wherein said detecting first and second intensity comprise capturing said incident light reflected from the semiconductor wafer at predefined time intervals.  
   
   
       24 . A computer-readable medium of instructions for detecting a transition interface between a first dielectric and an adjacent second dielectric in a semiconductor wafer during a polishing process, the instructions for controlling: 
 initiating the polishing process, said polishing process being implemented to remove the first dielectric material and expose the second dielectric material of the semiconductor wafer;    impinging an incident light of at least one predetermined wavelength on the semiconductor wafer;    detecting at least one first intensity of said incident light reflected from the semiconductor wafer at a first time;    detecting at least one second intensity of said incident light reflected from the semiconductor wafer at a second time;    determining a difference between the at least one first intensity and the at least one second intensity; and    providing a signal when the difference between the at least one first intensity and the at least one second intensity is above a predetermined threshold, wherein the signal indicates that the transition interface has been detected.    
   
   
       25 . The medium of  claim 24 , further comprising receiving a user input, wherein the user input defines the predetermined threshold.  
   
   
       26 . The medium of  claim 24 , further comprising, when the transition interface has been detected, terminating the polishing process.  
   
   
       27 . The medium of  claim 24 , further comprising plotting a graph of the at least one first intensity and the at least one second intensity as a function of time.  
   
   
       28 . The medium of  claim 27 , wherein the difference between the at least one first intensity and the at least one second intensity is calculated by determining a slope of the graph.  
   
   
       29 . The medium of  claim 24 , wherein at least one of the at least one predetermined wavelengths is approximately 400 nm to 900 nm.  
   
   
       30 . The medium of  claim 24 , wherein the incident light is white light.  
   
   
       31 . The medium of  claim 30 , further comprising detecting at least a first specific wavelength at the at least one first intensity, indicating the presence of the first dielectric material, and detecting at least a second specific wavelength at the at least one second intensity, indicating the presence of the second dielectric material.  
   
   
       32 . The medium of  claim 24 , wherein the first dielectric material is a DARC film layer, and the second dielectric material is a low-k film layer.  
   
   
       33 . The medium of  claim 24 , wherein said detecting first and second intensity comprise capturing said incident light reflected from the semiconductor wafer at predefined time intervals.  
   
   
       34 . A system of detecting a transition interface between a first dielectric material and an adjacent second dielectric material on a semiconductor wafer during a polishing process, the system comprising: 
 means for initiating the polishing process, said polishing process being implemented to remove the first dielectric material and expose the second dielectric material of the semiconductor wafer;    means for impinging an incident light of at least one predetermined wavelength on the semiconductor wafer;    means for detecting at least one first intensity of said incident light reflected from the semiconductor wafer at a first time;    means for detecting at least one second intensity of said incident light reflected from the semiconductor wafer at a second time;    means for determining a difference between the at least one first intensity and the at least one second intensity; and    means for providing a signal when the difference between the at least one first intensity and the at least one second intensity is above a predetermined threshold, wherein the signal indicates that the transition interface has been detected.    
   
   
       35 . The system of  claim 34 , further comprising means for terminating the polishing process when the transition interface has been detected.  
   
   
       36 . The system of  claim 34 , further comprising means for plotting a graph of the at least one first intensity and the at least one second intensity as a function of time.  
   
   
       37 . The system of  claim 34 , wherein at least one of the at least one predetermined wavelengths is approximately 400 nm to 900 nm.  
   
   
       38 . The system of  claim 37 , further comprising means for detecting at least a first specific wavelength at the at least one first intensity, indicating the presence of the first dielectric material, and detecting at least a second specific wavelength at the at least one second intensity, indicating the presence of the second dielectric material.  
   
   
       39 . The system of  claim 34 , wherein the first dielectric material is a DARC film layer, and the second dielectric material is a low-k film layer.  
   
   
       40 . The system of  claim 34 , wherein said detecting first and second intensity comprise capturing said incident light reflected from the semiconductor wafer at predefined time intervals.  
   
   
       41 . A polishing method for detecting a transition interface between a first dielectric material and an adjacent second dielectric material in a semiconductor wafer during a polishing process, the method comprising: 
 executing the polishing process, said polishing process being executed to remove a first dielectric material and expose a second dielectric material of the semiconductor wafer;    generating incident light of at least one predetermined wavelength upon a surface of the semiconductor wafer;    detecting at least one reflected light intensity from the surface of the second dielectric material;    analyzing the reflected light intensity to determine and produce a signal when the transition interface between the first dielectric and the second dielectric has been detected.    
   
   
       42 . The method of  claim 41 , further comprising, when the transition interface has been detected, terminating the polishing process.  
   
   
       43 . The method of  claim 41 , further comprising plotting a graph of the at least one first intensity and the at least one second intensity as a function of time.  
   
   
       44 . The method of  claim 43 , wherein the difference between the at least one first intensity and the at least one second intensity is calculated by determining a slope of the graph.  
   
   
       45 . The method of  claim 41 , wherein at least one of the at least one predetermined wavelengths is 400 nm.  
   
   
       46 . The method of  claim 41 , wherein the incident light is multi-wavelength light.  
   
   
       47 . The method of  claim 46 , further comprising detecting at least a first specific wavelength at the at least one first intensity, indicating the presence of the first dielectric material, and detecting at least a second specific wavelength at the at least one second intensity, indicating the presence of the second dielectric material.  
   
   
       48 . The method of  claim 41 , wherein the first dielectric material is a DARC film layer, and the second dielectric material is a low-k film layer.