Lucent Technologies Inc.

Jeffrey Alan Gregus

Yinon Degani

Richard A Gottscho

Po-Yen Lu

The specification describes techniques for applying under bump metallization (UBM) for solder bump interconnections on IC chips with Al bonding sites. The UBM of the invention comprises a copper layer applied directly to the aluminum bonding sites. Reliable bonds are obtained if the Al surface is a nascent surface. Such a surface can be provided by back sputtering an aluminum bonding site, or by a freshly sputtered aluminum layer. The copper layer is deposited on the nascent aluminum surface in e.g. a cluster tool without breaking vacuum. The UBM can be patterned using subtractive techniques.

Flip chip metallization

The present invention is predicated on applicants' discovery that inhomogeneity in films deposited on heated heterogeneous substrates can be substantially reduced by patterning the large area metal structures. Specifically, metal structures having areas in excess of about 2 mm.sup.2 are patterned so that the metal is within 1 mm of a metal edge. Thus, for example, a normally solid chromium bonding pad on a glass substrate is conveniently made as a patterned, open grid of 1 mm chromium lines. With such patterning, a subsequently deposited layer of silicon nitride has enhanced homogeneity over a large area, including enhanced uniformity of etching rate.

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Bethlehem, PA, United States of America

Jeffrey Alan Gregus