Photolithography at the Limits of Optical Resolution

Abstract

The continuous miniaturization in microelectronics requires advanced materials and processes that allow millions of electronic components to be integrated on a single chip of less than 1 cm2. The resolution of structures in the half and even quarter micron region is performed by the photolithographic process, i.e. the patternwise exposure of light-sensitive photoresist layers that alter solubility in developers when exposed to light. A recently developed bilayer photoresist consists of specifically functionalized anhydride-containing polymers and photoactive dissolution inhibitors. Within the CARL (Chemical Amplification of Resist Lines) process, the anhydride moieties in the resist enable room-temperature silylation with bisamino-siloxanes in aqueous based solvents that enhances oxygen-plasma etch resistance and creates widened structures. Thus, the resolution capability of optical exposure tools can be used to the full extent, and even structures beyond the optical resolution limit become accessible. Copolymerization of maleic anhydride with Boc-maleimide or tert-butyl methacrylate yields polymers for highly sensitive acid-catalyzed deep UV resists.