Two-step hydrogen plasma treatment on low dielectric constant (low-k) fluorinated amorphous carbon films (a-C:F) was conducted to improve their thermal stability and reduce the damage caused by the patterning processes. First, hydrogen plasma treatment repairs imperfect bonds of as-deposited a-C:F films, stabilizing their chemical structures and increasing their resistance against elevated thermal stresses. After this passivation process, an additional hydrogen plasma treatment was applied to a-C:F films that had been etched using a mixture of N-2+O-2+CHF3, enabling sub-130 nm damascene trenches to be patterned and repairing the chemical structures destroyed by the etching plasma.