Methods and systems for detecting a presence of blobs on a specimen during a polishing process

Abstract

Systems and methods for detecting a presence of blobs on a specimen are provided. One method may include scanning measurement spots across a specimen during polishing of the specimen. The method may also include determining if the blobs are present on the specimen at the measurement spots. Each of the blobs may include unwanted material disposed upon a contiguous portion of the measurement spots. In some instances, the blobs may include copper. In some embodiments, scanning the measurement spots may include measuring an optical property and/or an electrical property of the specimen at the measurement spots. Another embodiment includes dynamically determining a signal threshold distinguishing a presence of the blobs from an absence of the blobs. An additional embodiment includes determining an endpoint of polishing if, for example, blobs are not determined to be present on the specimen.

1 . A method for detecting a presence of blobs on a specimen, comprising: 
 scanning measurement spots in a line across the specimen during polishing of the specimen; and    determining if blobs are present on the specimen at the measurement spots.    
   
   
       2 . The method of  claim 1 , wherein each of the blobs comprises unwanted material disposed upon a contiguous portion of the measurement spots.  
   
   
       3 . The method of  claim 1 , wherein each of the blobs comprises unwanted material formed upon a contiguous portion of the measurement spots, and wherein a height of each of the blobs varies across the contiguous portion.  
   
   
       4 . The method of  claim 1 , wherein each of the blobs comprises unwanted material formed upon a contiguous portion of the measurement spots, and wherein the contiguous portion comprises a lateral dimension within a predetermined range of lateral dimensions.  
   
   
       5 . The method of  claim 1 , wherein the blobs comprise copper.  
   
   
       6 . The method of  claim 1 , further comprising dynamically determining a signal threshold distinguishing a presence of the blobs from an absence of the blobs.  
   
   
       7 . The method of  claim 1 , further comprising dynamically determining a signal threshold distinguishing a presence of the blobs from an absence of the blobs, wherein said determining if the blobs are present comprises comparing output signals generated by said scanning to the signal threshold to determine if a portion of a blob is present on the measurement spots.  
   
   
       8 . The method of  claim 1 , wherein the line comprises substantially an entire lateral dimension of the specimen.  
   
   
       9 . The method of  claim 1 , wherein said scanning comprises scanning the line across the specimen in a plurality of passes such that the measurement spots extend across an area approximately equal to an area of the specimen.  
   
   
       10 . The method of  claim 1 , wherein said scanning comprises scanning the line across the specimen in at least two passes, the method further comprising detecting structures on the specimen from one or more output signals generated by said scanning.  
   
   
       11 . The method of  claim 1 , further comprising identifying structures on the specimen having a lateral dimension of less than about 1 μm from one or more output signals generated by said scanning.  
   
   
       12 . The method of  claim 1 , further comprising determining an endpoint of said polishing if the blobs are not determined to be present on the specimen.  
   
   
       13 . The method of  claim 1 , further comprising determining an approximate endpoint of said polishing if the blobs are not determined to be present on the specimen and altering a parameter of said polishing in response to the approximate endpoint such that the measurement spots extend across an area approximately equal to an area of the specimen.  
   
   
       14 . The method of  claim 1 , further comprising determining an approximate endpoint of said polishing if the blobs are not determined to be present on the specimen and reducing a speed of said polishing in response to the approximate endpoint.  
   
   
       15 . The method of  claim 1 , further comprising determining an approximate endpoint of said polishing if the blobs are not determined to be present on the specimen and altering a parameter of said polishing in response to the approximate endpoint to reduce dishing of the specimen.  
   
   
       16 . The method of  claim 1 , further comprising determining an approximate endpoint of said polishing if the blobs are not determined to be present on the specimen and altering a parameter of said polishing in response to the approximate endpoint to reduce erosion of the specimen.  
   
   
       17 . The method of  claim 1 , wherein said scanning comprises measuring an optical property of the specimen at the measurement spots.  
   
   
       18 . The method of  claim 1 , wherein said scanning comprises measuring optical reflectivity of the specimen at the measurement spots.  
   
   
       19 . The method of  claim 1 , wherein said scanning comprises measuring an electrical property of the specimen at the measurement spots.  
   
   
       20 . The method of  claim 1 , wherein said scanning comprises measuring an electrical property of the specimen at the measurement spots with an eddy current device.  
   
   
       21 . The method of  claim 1 , wherein said scanning comprises measuring optical reflectivity and an electrical property of the specimen at the measurement spots.  
   
   
       22 . The method of  claim 1 , wherein an average lateral dimension of the measurement spots is less than about 6 mm.  
   
   
       23 . The method of  claim 1 , wherein said determining comprises modeling one or more output signals generated by said scanning on a time basis.  
   
   
       24 . The method of  claim 1 , further comprising determining a characteristic of said polishing at the measurement spots from one or more output signals generated by said scanning.  
   
   
       25 . The method of  claim 1 , further comprising determining a characteristic of said polishing at the measurement spots from one or more output signals generated by said scanning and altering a parameter of said polishing in response to the characteristic of said polishing to reduce within specimen variation of the characteristic.  
   
   
       26 . The method of  claim 1 , further comprising altering a parameter of said polishing in response to the determined presence of the blobs on the specimen using a feedback control technique.  
   
   
       27 . The method of  claim 1 , further comprising altering a parameter of an instrument coupled to a polishing tool in response to the determined presence of the blobs on the specimen using a feedforward control technique.  
   
   
       28 . The method of  claim 1 , further comprising altering a parameter of said polishing in response to the determined presence of the blobs on the specimen using an in situ control technique.  
   
   
       29 . The method of  claim 1 , wherein said polishing comprises contacting a surface of the specimen with a slurry, and wherein said determining comprises modeling an effect of the slurry on one or more output signals generated by said scanning and reducing the effect of the slurry on the one or more output signals.  
   
   
       30 . The method of  claim 1 , further comprising generating a two-dimensional map of the blobs present on the specimen as a function of relative locations of the measurement spots.  
   
   
       31 . The method of  claim 1 , further comprising generating a two-dimensional map of the blobs present on the specimen as a function of absolute locations of the measurement spots.  
   
   
       32 . The method of  claim 1 , further comprising fabricating a semiconductor device on the specimen.  
   
   
       33 .- 67 . (canceled)  
   
   
       68 . A method for detecting a presence of blobs on a specimen, comprising: 
 scanning measurement spots in a line across the specimen during processing of the specimen; and    determining if blobs are present on the specimen at the measurement spots.    
   
   
       69 . The method of  claim 68 , wherein said processing comprises removing material from the specimen.  
   
   
       70 . The method of  claim 68 , wherein said processing comprises etching the specimen.  
   
   
       71 . The method of  claim 68 , wherein said processing comprises cleaning the specimen.  
   
   
       72 .- 75 . (canceled)