Designing EUV negative tone resist and underlayer approaches exhibiting 14nm half-pitch resolution

The main challenge in developing a suitable EUV photoresist, particularly for high Numerical Aperture (NA) EUV lithography anticipated for late 2024, lies in the Resolution, Line Width Roughness, and Sensitivity (RLS) trade-off. PiBond has been actively addressing this challenge by developing silicon photoresist (SiPR) based on chemically modified HSQ siloxane chemistry, consisting of a single polymer component. This resist, a non-metal negative tone, high Si-containing, employs the industry-standard TMAH developer. Previously, we achieved a resolution of 32nm pitch with a dose of 170mJ/cm2 and a Line Width Roughness (LWR) of 5.3nm. In this study, we synthesized a novel chemically modified HSQ-type siloxane resist to enhance RLS characteristics, assessing its performance using both Electron Beam Lithography (EBL) and EUVL. Utilizing the EUV Interference Lithography tool at PSI, we obtained a 28nm pitch resolution with an improved LWR of approximately 3.2nm, while controlling the dose-to-size to about 120mJ/cm2. Furthermore, by employing a suitable silicon hard mask underlayer developed in-house, we further enhanced sensitivity by 24% at 28nm pitch and 38% at 30nm pitch resolution. Crucially, we established correlations between EBL and EUV for our SiPR, leveraging the accessibility of EBL compared to EUV tools. Leveraging these correlations, we effectively utilized EBL to investigate the newly synthesized resist and optimize processing conditions. Our findings demonstrate the significant impact of both resist functionalization and processing conditions on the final lithography performance.