Browse Prior Art Database

Selective Etching of Copper in the Presence of Nickel and Molybdenum

IP.com Disclosure Number: IPCOM000122668D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Boecker, J: AUTHOR [+4]

Abstract

During the production of high-end computers, part of the wiring of the multichip multilayer ceramic carrier is fabricated in thin-film technology on the module surface. The conductor pattern is produced by photolithography, and the previously blanket sputtered or deposited copper layer is etched in a wet-chemical process.

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Selective Etching of Copper in the Presence of Nickel and Molybdenum

      During the production of high-end computers, part of the
wiring of the multichip multilayer ceramic carrier is fabricated in
thin-film technology on the module surface. The conductor pattern is
produced by photolithography, and the previously blanket sputtered or
deposited copper layer is etched in a wet-chemical process.

      To prevent corrosion and adverse effects during copper etching,
the vias containing molybdenum are electrolessly nickel-plated.  By
metal diffusion, yielding a 0.5 - 1 mm thick Ni/Mo diffusion zone,
the nickel and the molybdenum are satisfactorily bonded to each
other.  While the conventional electrolytes used for copper etching
attack the diffusion zone in particular, they have no effect on the
nickel material.  If the diffusion zone is dissolved completely,
contact between the nickel and the underlying molybdenum conductors
may be lost.

      Underetching occurs whenever the eletrolyte contacts the nickel
layer and penetrates same.  At a layer thickness of 2 mm, it may be
assumed that the surface is not fully continuous, as porosity
increases the thinner the nickel layer becomes.

      If defects are found during the production of a wiring pattern
of, say, copper, it is expedient to reuse the ceramic carrier and to
chemically remove the copper pattern layer.  As this may lead to
local underetching, the layer structure surrounding the nickel has to
be...