Novel interconnect structures possessing a dense OSG material for 90 nm
and beyond BEOL technologies in which a low power density oxygen-based
de-fluorination plasma process is utilized to increase NBLoK selectivity
are presented. These BEOL interconnect structures are capable of
delivering enhanced reliability and performance due to the reduced risk
of Cu exposure and hence electromigration and stress migration related
failures. The oxygen based de-fluorination process is such that the
plasma conditions employed {low power density (<0.3 Wcm.sup.-2);
relatively high pressure (>100 mT); negligible ion current to wafer
surface (applied source frequency only)} facilitate a physical expulsion
of residual fluorine present on the chamber walls, wafer surface, and
within the via structure; thus, minimizing the extent of NBLoK etching
that can occur subsequent to removing polymeric byproducts of via
etching.