Amorphous carbon step coverage improvement applied to advanced hard mask for lithographic application

Poor deposited step coverage (S/C) of carbon hard mask (HM) at alignment and overlay masks can cause worse overlay signal and further rework performance. A much better step coverage film can be obtained using C₂H₂ as precursor owing to superior sticking coefficient (higher C/H ratio). This C₂H₂ base amorphous (a-C) film property and etch selectivity are also compatible with other precursors at the same time. As to the rework ability, it improved a lot and the pattern is still clear even after five times of rework.