Bottom anti-reflective coating for hyper NA process: theory, application and material development

To obtain high resolution lithography in semiconductor industry for 45 nm node and beyond, 193 nm immersion lithography is a state-of-the-art technology. The hyper NA process in immersion technology requires unique design of bottom antireflective coating (BARC) materials to control reflectivity and improve lithography performance. Based on simulations, high n low k materials are suitable for BARC applications in hyper NA process. This paper describes the principle of the material development of high n low k BARC materials and its applications in hyper NA lithography process. The BARC material contains a dye with absorbance maximum lower than the exposure wavelength, e.g 170-190 nm. The enhancement of n values due to anomalous dispersion was illustrated by dispersion curves of new BARC materials. The relationship of the optical indices of BARC materials at 193 nm with the absorption properties of dyes was investigated. The novel high n low k materials have shown excellent lithography performances under dry and immersion conditions.