Method for control of etch profile

• US 4,671,849 A
• Filed: 05/06/1985
• Issued: 06/09/1987
• Est. Priority Date: 05/06/1985
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Chen, Lee, Mathad, Gangadhara S.
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Lithgow, Thomas M.
• Application Number:
  US06/730,976
• Time in Patent Office: 764 Days
• Field of Search: 156/643, 156/644, 156/646, 156/653, 156/657, 156/662, 204/192 E, 430/313, 430/317, 430/323
• US Class Current: 438/713
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

A method for precisely controlling the profile of an opening etched in a layer of material, for example, an insulating layer. In one embodiment, wherein a silicon dioxide layer is reactive ion etched through a photoresist mask, the concentration of a reactive species in an etchant gas is changed during the etching process to change the slope of the opening, the upper sidewall portion of the opening having a shallow slope and the lower sidewall portion of the opening having a steep slope. The final slope of the opening formed by this method is independent of the initial slopes of the images developed in the photoresist mask.

Claims

1. A method for etching openings having a desired sidewall profile in a silicon dioxide layer, comprising:

forming a photoresist mask layer on said silicon dioxide layer, said mask layer having an opening therethrough at the desired location of each opening to be etched in said silicon dioxide layer;

plasma etching said silicon dioxide and photoresist layers in an etchant gas consisting essentially of CF₄ and CHF₃ ; and

decreasing the percentage gas configuration of CHF₃ during said plasma etching from an initial concentration greater than about 25% by volume to form an etched opening in said silicon dioxide layer having a shallower sidewall slope at its upper portion than the slope at its lower portion.

2. The method of claim 1 wherein the final percentage gas concentration of CHF₃ is between about 5% and 25% by volume.

3. The method of claim 2 wherein said plasma etching is performed in a plasma reactor having an active volume less than about 40 cc., at an RF power of at least about 200 watts and a pressure of at least about one torr.