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Alternate Method for Etching Copper Seed Layers

IP.com Disclosure Number: IPCOM000110487D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 35K

Publishing Venue

IBM

Related People

Graham, T: AUTHOR [+3]

Abstract

An alternate solution for etching copper that is commonly used as a plating base as well as conductor material in microelectronic interconnection applications is described. Commonly used solutions are usually chloride containing and are very aggressive and damaging to other materials in the interconnection structures (such as solder pads) and leave undesirable ionic residues that can potentially initiate corrosion. Less aggressive etchants, typically based on oxidants, such as ammonium persulfate, are too slow in etching copper and require heating to enhance the etch rates. They are therefore not desirable for volume manufacturing applications. It was found that an etching solution comprising phosphoric acid (50%), acetic acid (40%) and nitric acid (10%) provides an ideal balance between these extremes.

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Alternate Method for Etching Copper Seed Layers

      An alternate solution for etching copper that is commonly used
as a plating base as well as conductor material in microelectronic
interconnection applications is described.  Commonly used solutions
are usually chloride containing and are very aggressive and damaging
to other materials in the interconnection structures (such as solder
pads) and leave undesirable ionic residues that can potentially
initiate corrosion.  Less aggressive etchants, typically based on
oxidants, such as ammonium persulfate, are too slow in etching copper
and require heating to enhance the etch rates.  They are therefore
not desirable for volume manufacturing applications.  It was found
that an etching solution comprising phosphoric acid (50%), acetic
acid (40%) and nitric acid (10%) provides an ideal balance between
these extremes.  Copper seed layers are etched at room temperature at
a rate of 1mm/min without attacking adjoining regions of Pb-Sn solder
pads.  Further, there are no discernible surface residues after
rinsing the samples in de-ionized water and ethanol.  Since the
solutions do not contain halides, serious corrosion concerns are not
anticipated.

      Disclosed anonymously.