Comparison of Al- and Hf-based hybrid photoresists grown by molecular layer deposition for extreme ultraviolet lithography

The continued downscaling of electronic device dimensions requires the development of high-performance resist materials for advanced lithographic patterning. In this study, we examine Al-based hybrid “alucone” thin films grown by molecular layer deposition (MLD) for application to extreme ultraviolet (EUV) lithography and compare their resist properties with those of previously studied Hf-based MLD hybrid “hafnicone.” Both alucone films presented here—standard alucone and oxygen-rich alucone—are deposited using the precursors trimethylaluminum and ethylene glycol. Using electron-beam lithography as a proxy for EUV, we demonstrate that alucone behaves as a negative-tone resist capable of resolving line widths down to ∼20 nm. It is found that the sensitivity of oxygen-rich alucone is 4800 μC/cm² using 0.125M HCl as the developer, whereas standard alucone is somewhat less sensitive. The resolution of alucone is higher than that of hafnicone, although the sensitivity is poorer. By performing x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, we investigate the degradation mechanism of standard alucone and compare this mechanism to that of hafnicone. We rationalize the observed differences in resist behavior between hafnicone and alucone by considering the oxophilicity of the metal atom in the respective thin films. This study provides a deeper understanding of the relationship between MLD film chemistry and irradiation responsiveness, which can help advance the optimization of resist materials for microelectronics fabrication.