Patterning of porous SiOCH using an organic mask: Comparison with a metallic masking strategy

The etching of sub-100-nm porous dielectric trenches has been investigated using an organic mask. The etching process that is performed in an oxide etcher is composed of three steps: a thin dielectric antireflective coating (DARC) layer (silicon containing layer) is etched in the first step, the organic mask [carbon-based layer (CL)] is opened in the second step, and the dielectric layer is etched in the last step. The DARC layer is open in a fluorocarbon-based plasma (CF4∕Ar∕CH2F2) and the main critical dimension issue is the critical dimension control of the trench, which can be adjusted by controlling the amount of polymer generated by the etching chemistry (% of CH2F2). The CL is etched using NH3 based plasmas, leading to straight trench profiles. For dielectric patterning, the etch process results from a delicate trade-off between passivation layer thickness and mask faceting. This is driven by the polymerizing rate of the plasma (% of CH2F2) which controls the trench width. Using an optimized etchin...