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Selective Etching of Copper

IP.com Disclosure Number: IPCOM000100416D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Datta, M: AUTHOR [+3]

Abstract

An electrochemical technique for selective etching of copper in the presence of chromium, nickel and gold is described. From an electrochemical point of view each metallic layer has a certain characteristic polarization behavior which remains unaffected by the fact that the layer is in contact with another material. This situation is similar to the phenomena observed for anodic dissolution of different phases in a heterogeneous alloy (1,2). By comparing the anodic polarization curves in an appropriate electrolyte, it is possible to select a potential at which a particular metal can be preferentially dissolved.

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Selective Etching of Copper

       An electrochemical technique for selective etching of
copper in the presence of chromium, nickel and gold is described.
From an electrochemical point of view each metallic layer has a
certain characteristic polarization behavior which remains unaffected
by the fact that the layer is in contact with another material.  This
situation is similar to the phenomena observed for anodic dissolution
of different phases in a heterogeneous alloy (1,2).  By comparing the
anodic polarization curves in an appropriate electrolyte, it is
possible to select a potential at which a particular metal can be
preferentially dissolved.

      Chromium, nickel and gold passivate easily in aqueous
electrolytes, and anodic dissolution of these metals occurs only at
relatively high potentials.  Copper, on the other hand, is relatively
active and dissolves at high rates even at low anodic potentials.
This behavior is shown in the figure which shows the anodic
polarization curves for copper, chromium, nickel and gold in 3M
sodium nitrate solution.  The data of the figure permits one to
select an anodic potential in the potential range between -0.3 volt
and +0.5 volt (vs. a mercury sulfate reference electrode) where
anodic dissolution of copper takes place at high rates while the
chromium, nickel and gold layers remain completely passive. Similar
polarization behavior is obtained in several other electrolytes
containing oxidizing anions over a wide range of pH and
concentration.  Exa...