Fluorinated Polymethacrylates as Highly Sensitive Non-chemically Amplified E-beam Resists
In an effort to improve upon the sensitivity of commercial non-chemically amplified e-beam resists, four polyacrylates functionalized with alpha-CF3 and/or CH2CF3 alkoxy substituents were studied. The alpha-CF3 substituent is known to increase backbone-scission efficiency while simultaneously eliminating acidic out-gassing and cross-linking known to occur in alpha-halogen substituted polyacrylates. Contrast curves for the polymeric alpha-CF3 acrylates, generated through e-beam exposure, showed the resists required an order of magnitude less dose than the current industry-standards, PMMA and ZEP. The fundamental sensitivity of these materials to backbone scissioning was determined via Co-60 gamma-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 PMTFMA was found to be 2.8x and 4.0x faster, respectively, than PMMA.