An improved and new process for fabricating self-aligned metal barriers by atomic
layer deposition, ALD, capable of producing extremely thin, uniform, and conformal
metal barrier films, selectively depositing on copper, not on silicon dioxide interlevel
dielectric, in multi-layer dual damascene trench/via processing. Silicon nitride
is presently used as a insulating copper barrier. However, silicon nitride has
a relatively high dielectric constraint, which deteriorates ICs with increased
RC delay. Copper metal barriers of niobium and tantalum have been deposited by
atomic layer deposition on copper. With high deposition selectivity, the barrier
metal is only deposited over copper, not on silicon dioxide, which eliminates the
need of an insulating barrier of silicon nitride.
