Browse Prior Art Database

Method and Materials for Terminal Metals

IP.com Disclosure Number: IPCOM000108265D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Cook, HC: AUTHOR [+3]

Abstract

Both titanium (Ti) and an overlapping chromium (Cr) layer are used in a lift-off terminal metals structure resulting in low electrical resistance and improved reliability following multiple solder reflow at chip connections.

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Method and Materials for Terminal Metals

       Both titanium (Ti) and an overlapping chromium (Cr) layer
are used in a lift-off terminal metals structure resulting in low
electrical resistance and improved reliability following multiple
solder reflow at chip connections.

      Referring to Fig. 1, photoresist 2 is applied and terminal
metal via hole definition through insulating layer (or layers) 4 to
expose aluminum (Al) or Al alloy terminal metal 6 is performed as
usual.  Then Ti film 8, 100 to 500 Angstroms thick, is deposited at
ambient temperature.  Ti 8 on top of photoresist 2 is loosely
adherent to photoresist 2 and may be removed by a suitable method
before conventional stripping of photoresist 2.

      Referring to Fig. 2, terminal definition is performed using
high temperature (140 degrees Celsius) compatible photoresist 12 and
otherwise conventional photo and etching processes.
Chromium-copper-gold (CrCuAu) film 10 deposition is performed in a
conventional manner, i.e., holding substrate temperature at 14
degrees Celsius during Cr deposition for low stress film.  After
conventional lift-off removal of photoresist 12 and film 10 residing
on it, solder is deposited and reflowed by conventional means (not
shown). During the reflow process, the Ti reacts with Al in layer 6
and Cr in layer 10 to reduce and dissolve oxides, thereby creating
low interlayer resistance.  Cr overlaps and protects underlying Ti
from oxidation by external oxygen sources. ...