From Event: SPIE Advanced Lithography + Patterning, 2023
In this work we assess the effect of the change of counter-anions on the photolithography properties of butyl-Sn12 oxo hydroxo cages. The hydroxide anions were exchanged with tetrakis(pentafluorophenyl)borate (B(PFP)4)- and (phenyl) trifluoroborate (BF3Ph)- anions which exhibit a photoabsorption cross section at 92 eV that is similar to that of the butyl-Sn12 oxo hydroxo cages. The degradation of the EUV photoresist was monitored via in-situ EUV exposure followed by X-ray photoelectron spectroscopy (XPS) at the BEAR beamline (Elettra, Italy) at the C1s-edge. Both systems exhibit similar carbon losses of around 25% for 100 mJ/cm2 dose. The Sn12 cluster with acetate anions, as a reference compound, exhibit a loss of C1s XPS signal from the butyl chains of around 23% for the same 100 mJ/cm2 EUV exposure dose indicating a larger degradation of the Sn12 cluster for the latter. We also evaluated the patterning performance of the Sn12(B(PFP)4) resist via interference lithography at the XIL-II beamline (PSI, Switzerland) and found the positive tone character of the resist and its ability to write lines with 50 nm half pitch resolution for doses of 30 mJ/cm2. In contrast, Sn12(BF3Ph) acts as a sensitive negative tone resist, with doses of 12.5 mJ/cm2 sufficient to write 50 nm half pitch lines.
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Quentin Evrard, Najmeh Sadegh, Chao Chun Hsu, Nicola Mahne, Angelo Giglia, Stefano Nannarone, Yasin Ekinci, Michaela Vockenhuber, Akira Nishimura, Tsuyoshi Goya, Takuo Sugioka, and Albert M. Brouwer, "Influence of the anion in tin-based EUV photoresists properties," Proc. SPIE 12498, Advances in Patterning Materials and Processes XL, 124980Z (Presented at SPIE Advanced Lithography + Patterning: March 01, 2023; Published: 30 April 2023); https://doi.org/10.1117/12.2658498.