Multi-trigger resist: novel synthesis improvements for high resolution EUV lithography

Irresistible Materials (IM) is developing novel resist systems based on the Multi-trigger concept, which incorporates a dose dependent quenching-like behaviour. The Multi Trigger Resist is a non-metal based negative tone resist, and consists of a base molecule and a crosslinker, which represent the resist matrix, together with a photoacid generator (PAG). Previously presented MTR2 showed 16 nm half pitch lines patterned with a dose of 38 mJ/cm², giving a LER of 3.7 nm on the NXE3300. Since then, research has been undertaken to improve this resist. In particular we are focusing on improved RLS; reduced top-loss and wiggling at high aspect ratios; eliminating the antimony PAG and further reduction of chemical stochastics. In this study, we present the approaches that have been taken to attain these goals and the initial results. Using the EUV Interference Lithography tool at PSI, a multi trigger resist with a high absorbance non-metal element included in the resist matrix, MTR2627, has been patterned at a pitch of 28nm with an estimated dose of 53mJ/cm² and LER of 4.2nm. The LWR is improved in the low dose region, and results also show that a thicker film can be used without pattern collapse below pitch 32nm due to increased stiffness. Using the Berkeley MET tool, this resist matrix with a higher MTR ratio has patterned 24nm lines at a pitch of 48nm with an LER of 1.9nm with a dose of 65mJ/cm². Additionally, we present initial results for an MTR resist series where the antimony PAG has been replaced with a carbon based PAG.