The thermal stability of Cu interconnects fabricated by dry etching wi
th simultaneous formation of a self-aligned passivation film has been
investigated. The passivation film on the sidewall of the interconnect
s is composed of SiON free from impurities such as Cl. This film acts
as a barrier layer to prevent Cu from corroding and oxidizing during a
ny subsequent process, such as formation of a dielectric overcoating.
Using this etching process, the Cu interconnect of a TiN/Cu/TiN multil
ayered structure is formed. The resistivity of the Cu interconnects is
about 1.7-2.2 mu Omega cm in the width range 0.2-10 mu m and remains
unchanged on annealing up to 700 degrees C. Diffusion of Cu into the s
ubstrate is not observed up to 800 degrees C annealing. These results
demonstrate that the sidewall film prevents diffusion of Cu. Therefore
the Cu interconnect covered with TiN and the thick sidewall film is s
uitable for the ultralarge-scale integration process.