A method for forming an opening in an organic insulating layer by covering
the insulating layer with a bilayer containing a resist hard mask layer
and a resist layer on top of the resist hard mask layer. The bilayer is
patterned, and an opening is created by plasma etching the insulating
layer in a reaction chamber containing a gas mixture. The plasma etching
is controlled so that virtually no etch residues are deposited and so that
the side walls of the opening are fluorinated to enhance the anisotropy of
the etching. The gas mixture can be a mixture of a fluorine-containing gas
and an inert gas, a mixture of an oxygen-containing gas and an inert gas,
or a mixture of hydrogen bromide and an additive.
