Improving EUV underlayer coating defectivity using Point-Of-Use filtration

Extreme ultraviolet (EUV) lithography has gained momentum towards high-volume manufacturing (HVM) as the method of choice for sub-20 nm half-pitch device fabrication. Optimized EUV photoresists and an improved understanding of the EUV patterning mechanisms have made significant progress toward achieving improved resolution, line-width roughness (LWR), and sensitivity. In addition, introducing a thin EUV underlayer (UL) into the regular EUV materials stack enhances the overall performance of EUV resists and opens the process window. As with all other spin-on photochemicals, utilizing filtration at the point-of-dispense can effectively reduce coating defects of the EUV underlayer material. In this paper, we will describe our efforts to leverage different filtration parameters, including retention ratings and membrane materials, to understand their impact on EUV underlayer coating defects, and will present the characterization of coating defects in very thin films.