Browse Prior Art Database

Rework Process for Integrated Circuit Chip Pads

IP.com Disclosure Number: IPCOM000110868D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Berger, RG: AUTHOR [+4]

Abstract

A process is described for safe removal of pad metals comprised of titanium (Ti), nickel (Ni), copper (Cu), gold (Au) and lead/tin (Pb/Sn), all deposited on aluminum (Al) alloy lands through via holes in oxide/nitride/polyimide insulation layers. Polyimide is also removed, and standard processing is used to remake that insulation layer, via holes through it, and terminal metal pads for the silicon integrated circuits. All of the metals, intermetallics, and byproducts from the removal process are cleanly removed, thereby avoiding any corrosion or other failure mechanism in the reworked product.

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Rework Process for Integrated Circuit Chip Pads

      A process is described for safe removal of pad metals comprised
of titanium (Ti), nickel (Ni), copper (Cu), gold (Au) and lead/tin
(Pb/Sn), all deposited on aluminum (Al) alloy lands through via holes
in oxide/nitride/polyimide insulation layers.  Polyimide is also
removed, and standard processing is used to remake that insulation
layer, via holes through it, and terminal metal pads for the silicon
integrated circuits.  All of the metals, intermetallics, and
byproducts from the removal process are cleanly removed, thereby
avoiding any corrosion or other failure mechanism in the reworked
product.

      When misprocessing in final stages of wafer processing or high
levels of defects in terminal metals are detected, the following
process steps may be applied to selectively remove terminal metals
and intermetalics formed in processing.  First, Pb/Sn is removed
using a room temperature, 1:1 (by volume) mixture of glacial acetic
acid and 30% hydrogen peroxide.  Next, Cu/Au/Sn/Ni metals and
intermetallics are removed using a room temperature, 3:1 (by volume)
mixture of concentrated nitric acid (HNO[3]) and concentrated
hydrochloric acid (HCl).  Finally, titanium (Ti) and/or
titanium/nickel (Ti/Ni) intermetallics are removed using a mixture
comprised of 43:3:1 volume ratio of water, concentrated HNO[3], and
hydrofluoric acid (HF) at room temperature.

      Polyimide is removed by means of oxygen ashing and a s...