Dielectric plasma etch process with in-situ amorphous carbon mask with improved critical dimension and etch selectivity

A plasma etch process for successively different layers, including an anti-reflection coating (ARC), an amorphous carbon layer (ACL) and a dielectric layer, with successively different etch chemistries is performed in a single plasma reactor chamber. A first transition step is performed after etching the ARC by replacing the fluorine-containing process gas used in the ARC etch step with an inert species process gas. A flush step is performed after etching the ACL by replacing the hydrogen-containing process gas used in the ACL etch step with argon gas.