High-NA EUV lithography–scheduled to be implemented in a few years for high-volume manufacturing of extremely downscaled Si devices with 2 nm node and beyond–demands ultrathin organic-inorganic hybrid photoresists with high EUV sensitivity and etch resistance. In this work, we synthesized a positive-tone hybrid photoresist composed of PMMA infiltrated with molecular network of indium oxide by vapor-phase infiltration (VPI), an ex-situ inorganic hybridization method derived from atomic layer deposition, and evaluated its patterning characteristics by electron-beam and EUV lithography (EBL and EUVL). The hybrid resist featured significantly enhanced etch resistance under dry etching but also the critical doses of 300 uC/cm2 for EBL and 60 mJ/cm2 for EUVL, both largely comparable to those of PMMA. Unlike alumina infiltration in PMMA that has been demonstrated previously, it was found that the weak binding nature of trimethyl indium (TMIn), the gaseous precursor used to infiltrate indium oxide in PMMA matrix, to the carbonyl group in PMMA enabled a uniform distribution of the oxide content across the PMMA thickness. However, it also led to undesired residue in the developed regions due to the strong interaction between the Lewis-basic hydroxyl groups on the surface of starting Si substrate with infiltrated TMIn. The residue issue could be mitigated by passivating the Si surface by hexamethyldisilizane (HMDS) and combining the acid/base rinse and oxygen plasma descum. The results not only hint at the potential of VPI-based ex-situ hybridization in developing novel hybrid EUV photoresists but also highlight the technological details that must be addressed to enable high EUVL performance in the infiltrated hybrid resist system.
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