Novel technique to enhance etch selectivity of carbon antireflective coating over photoresist based on O-2/CHF3/Ar gas chemistry

A new antireflective coating (ARC), amorphous carbon (C-ARC), substituted f or inorganic ARC (SiON) is gaining attention in dynamic random access memor y processing as devices scale down, requiring more fine control of submicro n (<0.13 mu) patterning. A parametric study of enhancing etch selectivity o f C-ARC over photoresist was performed based on O-2/CHF3/Ar gas chemistry i n 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, he at treatment, and deposition temperature of the amorphous carbon. Fourier t ransform infrared data revealed that a bonding transformation occurred in t he 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 degrees C for 15 min, leading to a boost in the etch rate of C-ARC. An etch selecti vity of similar to0.8 of C-ARC over the photoresist was achieved with annea ling of the amorphous carbon. The presence of hydrogen radicals in the plas ma 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 con tent on the surface. The hydrogen behavior on the surface appeared to be th e dominant factor in controlling etch selectivity. The surface reaction mec hanism of amorphous carbon is also discussed. (C) 2001 American Vacuum Soci ety.