A new antireflective coating (ARC), amorphous carbon (C-ARC), substituted for inorganic ARC (SiON) is gaining attention in dynamic random access memory processing as devices scale down, requiring more fine control of submicron (<0.13 mu) patterning. A parametric study of enhancing etch selectivity of C-ARC over photoresist was performed based on O-2/CHF3/Ar gas chemistry in a capacitively coupled plasma tool. The etch rate of C-ARC is found to be strongly dependent on the formation of hydrogen radicals in the plasma, heat treatment, and deposition temperature of the amorphous carbon. Fourier transform infrared data revealed that a bonding transformation occurred in the C-ARC from sp(3) tetrahedral structure to sp(2) graphite structure when amorphous carbon is subjected to heat treatment in a furnace at 600 degreesC for 15 min, leading to a boost in the etch rate of C-ARC. An etch selectivity of similar to0.8 of C-ARC over the photoresist was achieved with annealing of the amorphous carbon. The presence of hydrogen radicals in the plasma produced a similar result, with C-ARC phase transition from sp(3) to sp(2) bonding. The deposition temperature of C-ARC determined the hydrogen content on the surface. The hydrogen behavior on the surface appeared to be the dominant factor in controlling etch selectivity. The surface reaction mechanism of amorphous carbon is also discussed.