Fluorinated polymethacrylates as highly sensitive nonchemically amplified e-beam resists

In an effort to improve on the sensitivity of commercial nonchemically amplified e-beam resists, four polyacrylates functionalized with -CF3 and/or CH2CF3 alkoxy substituents were studied. The -CF3 substituent is known to increase backbone-scission efficiency while simultaneously eliminating acidic outgassing and cross-linking known to occur in -halogen substituted polyacrylates. Contrast curves for the polymeric -CF3 acrylates, generated through e-beam exposure, showed that the resists required an order of magnitude less dose than the current industry standards, poly(methyl methacrylate) (PMMA) and ZEP. The fundamental sensitivity of these materials to backbone scissioning was determined via 60Co -ray irradiation. The chain scissioning, G(s), and cross-linking, G(x), values calculated from the resulting change in molecular weight demonstrated that all fluorinated resists possess higher G(s) values than either PMMA or ZEP and have no detectable G(x) values. Utilizing e-beam and EUV interference lithographies, the photospeed of poly(methyl -trifluoromethacrylate) (PMTFMA) was found to be 2.8× and 4.0× faster, respectively, than PMMA.