Spectral imaging of substrates

Abstract

Spectral imaging systems and methods are provided for monitoring a substrate during a chemical-mechanical planarization process. An example system includes a carrier configured to receive a substrate, and a platen configured to receive a polishing pad. The platen includes an aperture configured to pass light. The system also includes a frame that disposes the platen in any number of positions relative to the carrier. An optoelectronic system is coupled to the aperture, and the aperture passes light of the optoelectronic system to illuminate the substrate and passes reflected light from the substrate to the optoelectronic system. A processing system is coupled to the optoelectronic system and uses the reflected light to image the substrate as the polishing pad is polishing the substrate.

1 . A system comprising: 
 a carrier configured to receive a substrate;    a platen that includes an aperture configured to pass light, wherein the platen is configured to receive a polishing pad;    a frame that disposes the platen in a plurality of positions relative to the carrier;    an optoelectronic system coupled to the aperture, wherein the aperture passes light of the optoelectronic system to illuminate the substrate and passes reflected light from the substrate to the optoelectronic system; and    a processing system that uses the reflected light to image the substrate as the polishing pad is polishing the substrate.    
   
   
       2 . The system of  claim 1 , wherein the polishing pad includes an optical element that is positioned relative to the aperture to pass light to and from the aperture, wherein the optical element is optically transparent.  
   
   
       3 . The system of  claim 1 , wherein the optoelectronic system includes an illumination source coupled to the aperture.  
   
   
       4 . The system of  claim 3 , further comprising a first set of optical fibers coupled to the illumination source and the aperture.  
   
   
       5 . The system of  claim 1 , wherein the optoelectronic system includes an optical receiver coupled to the aperture, the optical receiver configured to receive the reflected light.  
   
   
       6 . The system of  claim 5 , wherein the optical receiver is a second set of optical fibers.  
   
   
       7 . The system of  claim 5 , wherein the optical receiver includes one or more of a receiver lens assembly and a receiver aperture.  
   
   
       8 . The system of  claim 5 , wherein the optical receiver includes a receiver aperture.  
   
   
       9 . The system of  claim 5 , further comprising a spectrometer lens assembly configured to receive light from the optical receiver.  
   
   
       10 . The system of  claim 9 , further comprising: 
 a wavelength-dispersive element configured to receive light from the spectrometer lens assembly; and    an imager configured to receive light from the wavelength dispersive element, wherein the imager captures a spectral image of a region of the substrate.    
   
   
       11 . The system of  claim 10 , wherein the imager is configured to capture a plurality of one-dimensional images from the reflected light of a pad-contacting surface of the substrate and to generate at least one two-dimensional image from the plurality of one-dimensional images.  
   
   
       12 . The system of  claim 11 , wherein the plurality of one-dimensional images represent at least a portion of a pad-contacting surface of the substrate during traversal of the aperture.  
   
   
       13 . The system of  claim 11 , wherein the two-dimensional image includes spectral images of at least a portion of a pad-contacting surface of the substrate during traversal of the aperture.  
   
   
       14 . The system of  claim 11 , wherein the one-dimensional images comprise line images.  
   
   
       15 . The system of  claim 11 , wherein the at least one two-dimensional image is derived from data points, wherein the data points are one or more of substantially contiguous and substantially non-contiguous.  
   
   
       16 . The system of  claim 10 , wherein the imager includes a spatial dimension and a spectral dimension for receiving dissected light from the wavelength-dispersive element, wherein the imager generates a two-dimensional data set for each of the one-dimensional images, a first dimension of the two-dimensional data set comprising a spatial dimension, and a second dimension of the two-dimensional data set comprising a spectral dimension.  
   
   
       17 . The system of  claim 16 , wherein the imager further comprises a processor configured to derive a frame from the two-dimensional data set.  
   
   
       18 . The system of  claim 1 , further comprising one or more of a spectrometer lens assembly configured to receive the reflected light from the substrate and a wavelength-dispersive element configured to receive light from the spectrometer lens assembly, and an imager configured to receive light from the wavelength dispersive element, wherein the imager captures a spectral image of a region of the substrate.  
   
   
       19 . The system of  claim 1 , wherein the aperture has a dimension greater than a diameter of the substrate, wherein the image includes an image of an entire surface of the substrate.  
   
   
       20 . The system of  claim 1 , wherein the aperture has a dimension approximately equal to a maximum planar dimension of a die of the substrate.  
   
   
       21 . The system of  claim 1 , wherein the aperture has a dimension less than a diameter of the substrate, wherein the image includes an image of a die of the substrate and an area smaller than an entire surface of the substrate.  
   
   
       22 . The system of  claim 1 , further comprising at least one motor coupled to rotate one or more of the platen and the carrier.  
   
   
       23 . The system of  claim 1 , wherein the polishing is chemical-mechanical planarization.  
   
   
       24 . The system of  claim 1 , wherein the polishing is orbital chemical-mechanical planarization, wherein the polishing pad undergoes orbital motion about a center point aligned with a rotational axis of the substrate.  
   
   
       25 . A method comprising: 
 securing a substrate to a carrier;    disposing a platen in a plurality of positions relative to the substrate, wherein the platen includes an aperture configured to pass light and a polishing pad; and    polishing the substrate with the polishing pad, the polishing including illuminating the substrate by passing light through the aperture, the polishing further including receiving reflected light from the substrate through the aperture, the polishing further including imaging the substrate using information of the reflected light.    
   
   
       26 . The method of  claim 25 , further comprising configuring the polishing pad to include an optical element that is positioned relative to the aperture to pass light to and from the aperture, wherein the optical element is optically transparent.  
   
   
       27 . The method of  claim 25 , further comprising passing the light to the aperture using a first set of optical fibers coupled to an illumination source.  
   
   
       28 . The method of  claim 25 , further comprising passing the reflected light from the aperture using an optoelectronic system that includes an optical receiver coupled to the aperture.  
   
   
       29 . The method of  claim 28 , wherein the optical receiver is a second set of optical fibers.  
   
   
       30 . The method of  claim 28 , wherein the optical receiver includes one or more of a receiver lens assembly and a receiver aperture.  
   
   
       31 . The method of  claim 28 , wherein the optical receiver includes a receiver aperture.  
   
   
       32 . The method of  claim 28 , further comprising a spectrometer lens assembly configured to receive light from the optical receiver.  
   
   
       33 . The method of  claim 32 , further comprising: 
 dispersing the received light from the spectrometer lens assembly according to a wavelength of the received light; and    capturing a spectral image of a region of the substrate from information of dispersed light.    
   
   
       34 . The method of  claim 33 , wherein the capturing includes capturing a plurality of one-dimensional images from the reflected light of a pad-contacting surface of the substrate and generating at least one two-dimensional image from the plurality of one-dimensional images.  
   
   
       35 . The method of  claim 34 , wherein the plurality of one-dimensional images represent at least a portion of a pad-contacting surface of the substrate during traversal of the aperture.  
   
   
       36 . The method of  claim 34 , wherein the two-dimensional image includes spectral images of at least a portion of a pad-contacting surface of the substrate during traversal of the aperture.  
   
   
       37 . The method of  claim 33 , further comprising receiving dispersed light in a spatial dimension and a spectral dimension, and generating a two-dimensional data set for each of the one-dimensional images, a first dimension of the two-dimensional data set comprising a spatial dimension, and a second dimension of the two-dimensional data set comprising a spectral dimension.  
   
   
       38 . The method of  claim 25 , wherein the aperture has a dimension that is one of greater than a diameter of the substrate, approximately equal to a maximum planar dimension of a die of the substrate, and less than a diameter of the substrate.  
   
   
       39 . The method of  claim 25 , further comprising rotating one or more of the platen and the carrier.  
   
   
       40 . The method of  claim 25 , wherein the polishing is chemical-mechanical planarization.  
   
   
       41 . The method of  claim 25 , wherein the polishing is orbital chemical-mechanical planarization.