Selective physisorption ALD-like process and selective PECVD process for smoothing metal organic resist using SO2

Extreme ultraviolet lithography enables the fabrication of sub-10 nm features, but several critical challenges remain related to the source/scanner, mask, and resist. One major issue with the extreme ultraviolet (EUV) resist is the poor line-edge roughness and line-width roughness that often result in low-quality pattern transfer to underlayers. Area selective deposition (ASD) is proposed as a corrective step for improving the EUV resist surface roughness. This study explores a strategy using physisorption in an atomic layer deposition (ALD)-like mode as a mechanism for ASD and compares the performance with a selective plasma-enhanced chemical vapor deposition (PECVD) process, as a foundational investigation on blanket films serving as an established proxy for patterned features. The precursor for both ASD processes is sulfur dioxide (SO2), which enables the selective deposition of sulfur-based films on Sn-based EUV resist while minimizing deposition on SiO2. A custom-designed ultrahigh vacuum chamber facilitates both ALD-like and PECVD processes. Modeling based on the London equation supports precursor selection, while in situ ellipsometry and angle-resolved XPS confirm selective deposition. The ALD-like process achieves a ∼10% reduction in surface roughness, while the PECVD process achieves up to 40% reduction without adversely affecting the EUV resist etch rate. These findings suggest that physisorption-based ALD-like and PECVD ASD processes are promising routes for surface smoothing in next-generation lithographic patterning.