EUV lithography using multi-trigger resist: performance improvements

Novel resist materials will be required to support high-NA EUV with its decreased depth of focus and requirement for thinner films with higher photon absorbance. Irresistible Materials (IM) is developing novel resists based on the multi-trigger concept. In a multi-trigger resist (MTR) multiple elements must be simultaneously activated to enable a catalytic reaction. MTR shows wide dose and patterning flexibility with both formulation ratio and material library changes. MTR Gen1 introduced tunable absorbance as high as 18 µm^-1. MTR Gen2 introduces alternative choices of molecules to increase the monomer activation rate, optimize the ring opening polymerization reactions and improve the chain termination selectivity. Here we present the lithographic performance at pitch 32nm hexagonal pillars where 16nm diameter pillars were patterned using a 20nm resist film at a dose of 43mJ/cm² with an unbiased LCDU of 2.8nm; or using a less sensitive formulation can be patterned at 74mJ/cm² with an unbiased LCDU of 2.7nm with fewer defects. We show staggered pillar results: pitch 36nm patterned at 51mJ/cm² to obtain a pillar diameter of 17.5nm with an unbiased LCDU of 2.2nm. Additionally, p32 contacts of 16nm diameter were patterned at 50mJ/cm² with a biased LCDU of 3.77nm. Using Gen 2.2 resist and a PEB of 85 °C, lines of 18.4nm width at pitch 40nm can be patterned using a 38nm film thickness and 43mJ/cm² dose. Performance improvements such as reduced roughness and defectivity can also be shown to be affected by choices such as underlayer, stack and developer. We also show that the choice of organic underlayer is key to reducing touching pillar defects, and that the use of silicon rather than organic underlayer for pillar patterning further reduces the defectivity.