Multiple level interconnect structures and methods for fabricating the interconnect
structures are disclosed. The interconnect structures may contain an interconnect
line, an electrolessly deposited metal layer formed over the interconnect line,
a via formed over the metal layer, and a second interconnect line formed over the
via. Often the metal layer contains a cobalt or nickel alloy and provides an etch
stop layer for formation of an opening corresponding to the via. The metal layer
may provide protection to the underlying interconnect line and may replace a traditional
protective dielectric layer. The metal layer is conductive, rather than dielectric,
and provides a shunt for passage of electrical current between the via and the
interconnect line. Similar metal layers may also be used within the interconnect
structures as via liner layers and via plugs.