A method for etching an organic anti-reflective coating (ARC) layer on a
substrate in a plasma processing system comprising: introducing a process
gas comprising ammonia (NH.sub.3), and a passivation gas; forming a
plasma from the process gas; and exposing the substrate to the plasma.
The process gas can, for example, constitute NH.sub.3 and a hydrocarbon
gas such as at least one of C.sub.2H.sub.4, CH.sub.4, C.sub.2H.sub.2,
C.sub.2H.sub.6, C.sub.3H.sub.4, C.sub.3H.sub.6, C.sub.3H.sub.8,
C.sub.4H.sub.6, C.sub.4H.sub.8, C.sub.4H.sub.10, C.sub.5H.sub.8,
C.sub.5H.sub.10, C.sub.6H.sub.6, C.sub.6H.sub.10, and C.sub.6H.sub.12.
Additionally, the process chemistry can further comprise the addition of
helium. The present invention further presents a method for forming a
bilayer mask for etching a thin film on a substrate, wherein the method
comprises: forming the thin film on the substrate; forming an ARC layer
on the thin film; forming a photoresist pattern on the ARC layer; and
transferring the photoresist pattern to the ARC layer with an etch
process using a process gas comprising ammonia (NH.sub.3), and a
passivation gas.