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Method of Doping CVD-AL With Cu

IP.com Disclosure Number: IPCOM000102025D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Related People

Colgan, EG: AUTHOR [+2]

Abstract

CVD-Al technology has been rapidly advancing (1) and allows filling of high aspect ratio cavities such as via holes. For improved electromigration resistance the CVD Al may be alloyed with Cu and a refractory metal layer added (2,3). The Cu reacts with the Al to form Al2Cu along the grain boundaries. The refractory metal layer reacts to form an aluminide at higher temperatures.

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Method of Doping CVD-AL With Cu

       CVD-Al technology has been rapidly advancing (1) and
allows filling of high aspect ratio cavities such as via holes. For
improved electromigration resistance the CVD Al may be alloyed with
Cu and a refractory metal layer added (2,3). The Cu reacts with the
Al to form Al2Cu along the grain boundaries.  The refractory metal
layer reacts to form an aluminide at higher temperatures.

      Discrete layers of refractory metals Cu, Al and CVD-Al are used
to achieve the desired electromigration-resistant structure after
annealing.  Initially Cr, Ta, or other refractory/adhesive metals
which do not react with Cu at low temperatures would be deposited,
followed by a layer of Cu. Both may be deposited by physical vapor
deposition.  The Cu layer thickness would be chosen to introduce the
correct amount of Cu into the Al after annealing.  This layer could
also be capped with Al as a seed layer for the CVD-Al growth.  Cu and
Al are known to react at low temperatures 4 so Al2Cu could form even
during CVD growth.  A higher temperature anneal would allow the Cu to
migrate through the Al layer and cause the refractory metal to react
with the Al.  Alternatively, the Cu layer thickness could be
increased in thickness so that a structure consisting of principally
Al2Cu would result.  This phase has a relatively low electrical
resistance and should be electro migration- and corrosion-resistant
as well.

      References
(1)  L. F. Tz...