Method for end point detection during plasma etching

• US 4,198,261 A
• Filed: 12/05/1977
• Issued: 04/15/1980
• Est. Priority Date: 12/05/1977
• Status: Expired due to Term

• Current Assignee: Gould Electronics Incorporated (Eternal Materials Co., Ltd.)
• Original Assignee: Gould, Inc. (Transdigm Group Incorporated)
• Inventors: Busta, Heinz H., Lajos, Robert E., Bhasin, Kul B.
• Primary Examiner(s): Massie, Jerome W.
• Application Number:
  US05/857,384
• Time in Patent Office: 862 Days
• Field of Search: 156/626, 156/643, 156/646, 156/345, 156/662, 156/655, 356/108, 356/114, 356/118, 356/364, 356/368, 356/381, 356/382
• US Class Current: 216/60
• CPC Class Codes: C23F 4/00 Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• CPC Class Codes: G01N 21/211 Ellipsometry optical thickness measurement G01B11/06

Abstract

A method and apparatus for detecting the end point of a plasma etching process comprising the use of an optical technique in which light is beamed on the layer to be etched and the resulting beam that is reflected and refracted is detected. Sharply different values of light intensity can be detected when the desired layer is etched and the next layer receives the light beam. A laser is preferably used to obtain an intense and substantially uniform frequency light source.

Claims

1. A method of detecting the end point of etching a first layer of material from a second layer of material wherein said materials have different indices of refraction, comprising the steps of:

mounting said materials in an etching chamber;

projecting a beam of light toward a portion of the material to be etched via a first polarizing filter;

reflecting said beam of light from said portion of the material to be etched;

following reflection, passing said beam of light toward a detector, via a second polarizing filter;

adjusting said first and second filters relative to said beam of light so that essentially no light will reach the detector following reflection and/or refraction from either said first or said second layer of material; and

detecting an abrupt change in the intensity of light reaching the detector due to the change in index of refraction from the first layer to the second, as an indication of said end point of etching.