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Optical techniques of measuring endpoint during the processing of material layers in an optically hostile environment

  • US 5,499,733 A
  • Filed: 09/16/1993
  • Issued: 03/19/1996
  • Est. Priority Date: 09/17/1992
  • Status: Expired due to Fees
First Claim
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1. A method of removing at least a portion of a layer that is carried on a first side of a substrate, comprising:

  • applying a material removing substance to an exposed surface of said layer but not to a second side of the substrate opposite said first side, said substance being characterized by modifying electromagnetic radiation incident thereon, whereby material is removed from said layer exposed surface but not from the second side of the substrate,directing a first beam of electromagnetic radiation against said second side of the substrate to said layer through said substrate, said first beam of electromagnetic radiation including a wavelength band to which each of said substrate and said layer is substantially transparent,receiving and detecting a second beam of electromagnetic radiation within said wavelength band that is a portion of said first beam that exits the second substrate side after reflection at boundary surfaces of said layer and said substrate, andconcurrently with material being removed from the exposed surface of the layer, monitoring a varying intensity of a component of the detected second beam which results from an interference between portions of the first beam reflected from said exposed surface and an underlying boundary surface.

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