Resolution, Line-Edge Roughness, Sensitivity Tradeoff, and Quantum Yield of High Photo Acid Generator Resists for Extreme Ultraviolet Lithography

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Ultrahigh loadings of photoacid generators (PAGs) in phenolic extreme ultraviolet (EUV) resists have generated the highest known film quantum yields (FQYs). We evaluate the performance of these resists in terms of resolution, line-edge roughness (LER), and sensitivity and collectively evaluate these three parameters (known as RLS) in terms of $K_{\text{LUP}}$ and $Z$-Parameter figures of merit. An analytical model describing the kinetics of photodecomposition was developed to explain the relationship between film quantum yield and PAG concentration. Resists were prepared using a broad range of concentrations of iodonium (DTBPI-PFBS), sulfonium (TPS-PFBS), and non-ionic (NDI-PFBS) PAGs. The model fits the experimental data (correlation coefficient $R^{2} = 0.998$, 0.994, and 0.995) and compares the rate at which electrons react with PAGs or recombine with holes. Resists prepared with 15--20 wt % of iodonium nonaflate PAG exhibit both high quantum yields and the best RLS performance as determined using both $K_{\text{LUP}}$ and $Z$-Parameter methodologies. The improvement in RLS performance correlates with the increase in FQY at higher PAG concentrations.
2011-03-25