MULTILAYER INORGANIC ANTIREFLECTIVE SYSTEM FOR USE IN 248 NM DEEP-ULTRAVIOLET LITHOGRAPHY

We propose a novel technique for reducing substrate reflections in 248 nm deep ultraviolet (DW) Lithography. The method we have developed ut ilizes a multilayer scheme comprised of layers of silicon rich oxide. Deposition of the film stack is carried out on a production ready PE-C VD tool in one continuous operation. The combining of multiple layers allows a gradual change in absorption thereby minimizing the reflectio n coefficient at the resist/ARC interface. The method of operation of these films is one of total absorption rather than the more common des tructive interference method of a single layer film which relies on ve ry tight thickness control. Absorption of the combined films is high e nough to be effective on even the most highly reflective substrates su ch as aluminum. Furthermore, this technique does not require the ARC f ilms to be tuned in their optical constants to accommodate the underly ing substrate. We have successfully patterned wafers with feature size s as small as 200 nm with no appreciable change in line width due to t he underlying topography. The multilayer ARC system has been successfu lly integrated into the gate level of a 0.25 mu m design rule-device w ith excellent results. A description of the films used, their optical properties, and results from experimental data, as well as numerical s imulations, will be reported. (C) 1996 American Vacuum Society.