×

Method and apparatus for controlling plasma etching

  • US 4,208,240 A
  • Filed: 01/26/1979
  • Issued: 06/17/1980
  • Est. Priority Date: 01/26/1979
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for etching a first layer of material to expose an underlying layer of a second material, comprising the steps of:

  • exposing said first layer to an etching medium;

    projecting a beam of coherent radiation onto the surface of said first layer, and in sequence said second layer, during etching;

    detecting radiation reflected from said first or second layer and producing a first analog signal in response thereto;

    determining the time derivative of said analog signal during successive intervals, each interval being of a length in time selectably chosen to ensure a maximum acceptable overetch beyond said first layer into said second layer;

    comparing the derivative determined for each successive interval to predetermined criteria indicative of the end-point of etching between said layers and providing a control signal upon achievement of end-point; and

    terminating said exposing step in response to said control signal.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×