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Etching Completion Detection by Displacement Reaction

IP.com Disclosure Number: IPCOM000085535D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Anderson, NC: AUTHOR

Abstract

At present, detecting the end point of an etching process of a dielectric thin film is difficult. A microscopic inspection is performed to observe a lack of color by diffraction in the thin residual layer. Etching for an excessive time to ensure removal can result in an attack on the underlying metallic layer.

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Etching Completion Detection by Displacement Reaction

At present, detecting the end point of an etching process of a dielectric thin film is difficult. A microscopic inspection is performed to observe a lack of color by diffraction in the thin residual layer. Etching for an excessive time to ensure removal can result in an attack on the underlying metallic layer.

It has been found that the end point of an etching process can be determined by using displacement reaction to cause a color change of the metallic underlayer, when the dielectric overlayer is etched away. For example, to determine the end point of etching through a layer of an insulating material such as silicon dioxide to expose a layer of ferrous material, an etchant of buffered hydrofluoric acid can be used with copper fluoride added to provide the indicating ions.

The presence of the copper ions will not interfere with the etching mechanism, and the displacement reaction will not occur until the underlaying metal film is exposed to the copper ions. The deposition of the copper can be easily noted by the color change to the bright copper. Routine sputter etching or etching in a dilute etching solution can then be performed, if desired, to remove the copper film.

To accomplish this end point determination by displacement reaction, it is necessary only that the underlying metal be higher on the electromotive series than the indicating ions in the solution. Further exampled are:. Dielectric Etchant Indi...