The invention provides a new multilevel interconnect structure of air gaps
in a layer of IMD. A first layer of dielectric is provided over a
surface; the surface contains metal points of contact. Trenches are
provided in this first layer of dielectric. The trenches are filled with
a first layer of nitride or disposable solid and polished. A second layer
of dielectric is deposited over the first layer of dielectric. Trenches
are formed in the second layer of dielectric, a second layer of nitride
or disposable solid is deposited over the second layer of dielectric. The
layer of nitride or disposable solid is polished. A thin layer of oxide
is deposited over the surface of the second layer of dielectric. The thin
layer of oxide is masked and etched thereby creating openings in this
thin layer of oxide, these openings align with the points of intersect of
the trenches in the first layer of dielectric and in the second layer of
dielectric. The nitride or removable solid is removed from the trenches.
The openings in the thin layer of oxide are closed off leaving a network
of trenches that are filled with air in the two layers of dielectric that
now function as the Inter Level Dielectric.