EUV lithography patterning using multi-trigger resist

Abstract

Research and development of EUV photoresists capable of supporting future requirements such as high-NA EUV continues. It is foreseen that, to contend with much higher photon-shot noise, resists will require high EUV absorbance to offset the need for thin films in high-NA, where depth of focus may be less than 20nm. We are developing a photoresist based on the multi-trigger concept, which seeks to suppress roughness using a new photoresist mechanism, and which is based on molecular rather than polymeric materials to maximize resolution. MTR Resist absorbance of greater than 18 μm-1 has been measured. Here we present recent NXE3400 results where, by modifying the PAG to optimize the reactions rates in the MTR mechanism, we have reduced the dose requirement compared to the orthodox high opacity MTR resists previously presented. Lines of 14 nm width at p28 nm can be patterned at a dose between 21 mJ/cm2 and 48 mJ/cm2 dependent on formulation ratio, with optimum LWR (3.9 nm, biased) occurring at 43 mJ/cm2 with a film thickness of 20.7 nm. Similarly, we present p34 pillars patterned between 21 mJ/cm2 and 59 mJ/cm2 doses for 17 nm diameter pillars, with a minimum LCDU for 19 nm diameter pillars of 3.05 nm occurring with a 21.7 nm FT at 58 mJ/cm2. The same resist can pattern p36 pillars at 52 mJ/cm2 with an LCDU of 3.44 nm at 18 nm diameter with no measured defects between 15.9 nm and 18.1 nm diameter. The impact of the substrate (such as use of various organic underlayers or SOG layers) on defectivity issues such as bridging or falling pillars will be presented here.