A dry etching technique for subquarter-micron Cu interconnects has bee
n developed. A self-aligned passivation film on sidewalls of Cu lines
is formed during etching. The thickness of the sidewall film composed
of SiON can be controlled precisely by the composition of the etching
gas mixture. The addition of NH3 to the etching gas mixture of SiCl4/C
l-2/N-2, results in a sidewall film free of chlorine. Therefore, the s
idewall film acts to protect Cu from oxidation and corrosion, and sust
ains the multilayered structure without film peeling during the fabric
ation process.