Methods of forming copper interconnects free from via-to-via leakage currents
and having low resistances are disclosed. In a first aspect, a barrier layer is
deposited on the first metal layer prior to copper oxide sputter-etching to prevent
copper atoms from reaching the interlayer dielectric and forming via-to-via leakage
current paths therein. In a second aspect, a capping dielectric barrier layer is
deposited over the first metal layer prior to sputter etching. During sputter-etching,
the capping dielectric barrier layer redistributes on the sidewalls of the interlayer
dielectric, preventing sputter-etched copper atoms from reaching the interlayer
dielectric and forming via-to-via leakage paths therein. In a third aspect, both
a capping dielectric barrier layer and a barrier layer are deposited over the first
metal layer prior to sputter-etching to prevent copper atoms produced during sputter-etching
from reaching the interlayer dielectric and forming via-to-via leakage paths therein.