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Optical emission spectroscopic techniques for monitoring etching

  • US 10,541,184 B2
  • Filed: 07/11/2017
  • Issued: 01/21/2020
  • Est. Priority Date: 07/11/2017
  • Status: Active Grant
First Claim
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1. A method of etching, the method comprising:

  • striking a plasma discharge;

    flowing a gas mixture comprising a hydrogen-containing gas and helium through the plasma discharge to form plasma effluents;

    flowing the plasma effluents through a plurality of apertures to a silicon layer on a substrate, the silicon layer having a first thickness;

    etching the silicon layer with the plasma effluents;

    measuring the intensity of emission from hydrogen from a reaction of plasma effluents with the silicon layer;

    measuring the intensity of emission from helium in the plasma effluents;

    integrating the intensity of the emission from helium over the duration the plasma effluents are being flowed to the silicon layer to obtain an integrated intensity of helium;

    integrating the intensity of the emission from hydrogen over the duration the plasma effluents are being flowed to the silicon layer to obtain an integrated intensity of hydrogen;

    calculating a parameter from the integrated intensity of hydrogen and the integrated intensity of helium;

    comparing the parameter to a reference value corresponding to a target thickness of silicon etched;

    extinguishing the plasma discharge when the integrated intensity is equal to or greater than the reference value to define a partially etched silicon layer on the substrate having a second thickness less than the first thickness.

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