Browse Prior Art Database

Combination Process for Final Metal Lines and Metal Terminals

IP.com Disclosure Number: IPCOM000110193D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 55K

Publishing Venue

IBM

Related People

Farrar, PA: AUTHOR [+2]

Abstract

Final metal lines, e.g., power buses, and bonding pads for chip terminals are formed simultaneously by a lift-off process. Final passivation (e.g., polyimide) is applied, terminal vias defined and etched open, and then solder is vacuum deposited through oversized holes in a deposition mask. After solder reflow, solder pulls back to edges of the via holes in the passivation layer and wetting only the bonding pad gold (Au) and copper (Cu) surface. Via holes in the passivation layer are made smaller than underlying bonding pads, thereby protecting edges of bonding pad metallurgy during via hole etching and any subsequent exposure to corrosives. Solder volume in terminals is a function of deposition mask hole area and vacuum deposition thickness.

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This is the abbreviated version, containing approximately 74% of the total text.

Combination Process for Final Metal Lines and Metal Terminals

      Final metal lines, e.g., power buses, and bonding pads for chip
terminals are formed simultaneously by a lift-off process.  Final
passivation (e.g., polyimide) is applied, terminal vias defined and
etched open, and then solder is vacuum deposited through oversized
holes in a deposition mask.  After solder reflow, solder pulls back
to edges of the via holes in the passivation layer and wetting only
the bonding pad gold (Au) and copper (Cu) surface.  Via holes in the
passivation layer are made smaller than underlying bonding pads,
thereby protecting edges of bonding pad metallurgy during via hole
etching and any subsequent exposure to corrosives.  Solder volume in
terminals is a function of deposition mask hole area and vacuum
deposition thickness.

      Fig. 1 is a planar view of a small region of surface of a
wafer having final metal line 10 near terminal bonding pad 12 and its
connecting line 14.  This metallurgy is vacuum deposited titanium
(Ti), then mixed Ti and copper (Cu), then pure Cu, and finally a thin
coating of gold (Au), when low temperature liftoff processing for
definition of metal patterns is used.  Chromium (Cr) may be
substituted for the Ti.  After lift-off processing is complete, final
passivation is applied over the entire surface and via holes are
defined by photo masking and etching to expose a portion of the top
surface of bonding pad metallurgy at the bottom 16 of the...