Transfer etching of bilayer resists in oxygen-based plasmas

Bilayer thin film imaging was shown to overcome limitations of conventional deep-UV single layer resist lithography, demonstrating sub 150 nm features. The O2-based transfer etch step is critical in the final image development, wherein the developed Si-containing imaging layer resist acts as a hard mask for pattern transfer into the thicker underlayer. The slow etching rate obtained and the lack of deprotection upon plasma exposure enables the use of thin imaging layer films. Pattern transfer enhancement with imaging resists with higher Si content was also demonstrated.