EUV lithography patterning using multi-trigger resist

Irresistible Materials is developing a novel photoresist for EUV lithography including high-NA patterning. A major concern for the key research area of high-NA EUV resists is that stochastics in such resist materials can lead both to roughness and defects causing failures, which means high-NA resists remain a priority research area. We are developing a photoresist based on the multi-trigger concept, which seeks to suppress line edge roughness using a new photoresist mechanism, and which is based on molecular rather than polymeric materials to maximize resolution. It also has relatively high EUV absorbance to increase photon capture despite the need for thin films in high-NA due to limited depth-of-focus. By modifying the MTM molecule, crosslinker and PAG, both individually and in combination, we can optimize the reaction rates in the MTR mechanism. Different combinations have been designated Gen 2.1 to Gen 2.6 and show an LWR improvement in Gen 2.4, 2.5 and 2.6 combinations. Here we present the lithographic performance at pitch 28nm dense line/space where 14.1 wide lines were patterned at 59mJ/cm2 with an unbiased LER of 2.09nm using a Gen 2.4 resist. We show hexagonal pillar results: pitch 32nm patterned at 42mJ/cm2 to obtain a pillar diameter of 16nm with an unbiased LCDU of 2.8nm; and additionally p32 pillars of 16nm diameter were patterned at 74mJ/cm2 with an unbiased LCDU of 2.7nm; and of 18.5nm diameter at 82mJ/cm2 with an unbiased LCDU of 2.3nm. We also show data which shows using a Gen 2.6 resist can reduce the LCDU of p32 hex pillars by 0.2nm and biased LWR of p28 l/s by 0.3nm compared to a comparable Gen 2.4 resist. Performance improvements such as reduced roughness and defectivity can also be shown to be affected by choices such as underlayer and developer. Additionally, the modification of the developer can be shown to influence the patterning performance of the resist at high resolution.