We have recently developed a bilayer resist system based on a methacrylic silicon-containing imageable layer and a UV curable copolymer undercoat which has exhibited 0.13 micrometers resolution for dense features and 0.12 micrometers resolution for isolated features after substrate etch. In this paper, we will discuss recent advancements in the design of the second generation bilayer resist. In particular, we will discuss the development of two new thermally curable undercoats for use in both 193 nm and 248 nm applications. The optical properties of these new materials have been optimized to reduce reflectivity at the desired wavelength.