Water-castable bottom antireflective coatings

Bottom antireflective coatings (BARCs) have been widely used in the industry to push i-line technology for a finer resolution. They have been shown to be highly effective in suppressing reflective notching and standing wave effects, in the reduction of the resist swing ratio and the improvement of the resist process latitude. One of the issues which has to be addressed by the design of any such coating is the problem of resist/bottom coat intermixing. The formation of an intermixing layer is usually suppressed either by crosslinking the BARC, or by using a polymer that is insoluble in the common resist casting solvents. This work describes a novel class of antireflective bottom coatings which are spin cast from the ultimate environmentally friendly solvent, water. The design requirements and philosophy of the water-borne polymer systems will be discussed. These polymers show high Ohnishi numbers, and the prediction of high etch rates is borne out by dry etch experiments. Polymer optical data have been obtained by UV spectroscopy and spectroscopic ellipsometry, and these optical and physical properties will be reported and related to their lithographic performance which is found to be equivalent to that of existing solvent-based antireflective coatings.