Performance data on new tunable attenuating PSM for 193nm and 157nm lithography

A new phase shifting film system based on tantalum and silicon dioxide is presented. The tantalum film works as a transmission control layer and furthermore as an etch stop layer due to its good etch selectivity. The silicon dioxide phase control layer is tuned to 180° phase shift. Excellent laser stability and chemical durability were already shown. The two layer system can be easily tuned to various transmission values for three different lithography wavelengths. Transmission and phase shift uniformity fulfill already the final production specifications according to ITRS. An optimized deposition process yields excellent film surface roughness values equal to an uncoated substrate. Defect density could be significantly reduced recently. First SEM pictures of structured films show promising results.