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Browse Prior Art Database

Surface Treatment for Tungsten to Facilitate Wire Bonding

IP.com Disclosure Number: IPCOM000101168D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 1 page(s) / 48K

Publishing Venue

IBM

Related People

Lane, R: AUTHOR [+3]

Abstract

Disclosed is a process for preparing the surface of tungsten to facilitate and enhance both thermosonic and ultrasonic bonding of gold or aluminum wire. The surface treatment consists of sputter etching tungsten in a vacuum to remove oxides followed by a vapor deposition of 1 to 2 microns of aluminum.

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This is the abbreviated version, containing approximately 69% of the total text.

Surface Treatment for Tungsten to Facilitate Wire Bonding

       Disclosed is a process for preparing the surface of
tungsten to facilitate and enhance both thermosonic and ultrasonic
bonding of gold or aluminum wire.  The surface treatment consists of
sputter etching tungsten in a vacuum to remove oxides followed by a
vapor deposition of 1 to 2 microns of aluminum.

      Conventional direct chip attach technology consists of bonding
a die to a rigid carrier that has interconnecting circuits etched on
it.  Electrical connections between the die and the carrier circuits
are made using wire bond technology.  Traditionally, the carrier
circuit material has been copper plated with nickel and then gold.
New applications require connections be made to an etched tungsten
circuit.  Conventional composite platings of copper, nickel and gold
on tungsten do not provide sufficient adhesion to insure a reliable
wire bond is made. Bonds made using this process typically fail at
the copper/ tungsten interface.  Vapor deposition of titanium on the
tungsten prior to plating with copper will promote better adhesion
and therefore better reliability, but this requires an additional
process step be added.  Titanium deposition is also expensive and
difficult to use in a manufacturing environment.

      Experimental results from a pilot manufacturing process has
shown that a superior metallurgical bond can be made between aluminum
and tungsten.  To achieve this bond, oxides...