Development of New Positive-Tone Molecular Resists Based on Fullerene Derivatives for Extreme Ultraviolet Lithography

We have developed and evaluated new chemically amplified molecular resists based on fullerene derivatives with an excellent solubility in a standard alkali developer for extreme ultraviolet (EUV) lithography. We controlled the electron acceptability of fullerene derivatives and applied photo-acid generators (PAGs) with a high electron acceptability through ionization by EUV irradiation. As a result, sensitivities of positive-tone molecular resists based on fullerene derivatives were markedly improved, and we succeeded in obtaining good resolution, by applying an organic underlayer substrate without pattern collapse. Delineations of 45 nm half pitch (hp) and line width roughness (LWR) of 5.7 nm were achieved at an exposure dose of 12.5 mJ/cm2 on the organic underlayer.