Dry development in an O2/SO2 plasma for sub-0.18 μm top layer imaging processes

Dry development using thin layer imaging (TLI) in either a bilayer approach or top surface imaging are currently investigated as viable alternatives to extend optical lithography to 0.13 mu m and below. This article describes a systematic study of dry development in a LAM TCP9400SE inductively coupled plasma etcher for both a single layer TLI resist process and for a bilayer resist process using O-2 and SO2/O-2 chemistries. The effect of the important machine parameters such as TCP power, bias power, O-2 and SO2 gas flows, on the process characteristics (etch rate, selectivity, uniformity, anisotropy) and on the lithographic performance (resolution, profile control, proximity) of a TSI process at 248 has been investigated by means of statistically designed experiments. As line edge roughness (LER) is a critical issue for TSI, the effect of the dry development conditions on LER have been quantified. The effect of temperature on profile control is also presented. In a second part of this article, these trends have been applied to the process optimization for a bilayer resist process at 193 nm. With an optimized dry development process, good profile control is demonstrated down to 0.12 mu m L/S resolution. (C) 1998 American Vacuum Society. [S0734-211X(98)07806-8].