Dry development of EUV resists via low electron temperature plasma

초록

Extreme ultraviolet (EUV, 13.5 nm) lithography enables nanoscale patterning of next-generation semiconductor devices. However, conventional chemically amplified resists (CARs) suffer from several limitations, including low EUV absorption, pattern collapse caused by capillary forces during wet development, and poor etch resistance. To address these challenges, metal-oxide resists (MORs) have been introduced, but pattern collapse is still reported at critical dimensions (CD) below 16 nm under wet development. In this study, we propose a dry development process based on low-electron-temperature plasma. This is achieved by suppressing the influx of high-energy electrons using a negatively biased mesh grid, while dissipating electron energy through collisions with neutral species, thereby maintaining a reduced electron temperature (Te). Under these conditions, the Sn–O network in the exposed regions remains stable, whereas the organic ligands in the unexposed regions are selectively removed, resulting in high development selectivity. When applied to SnO-based EUV photoresists with e-beam exposure and subsequent dry development, patterning stability is demonstrated for CDs in the range of 15–100 nm. Furthermore, the dry development exhibits line-edge roughness (LER) comparable to that of wet development (~3 nm, 3σ), and improved local critical dimension uniformity (LCDU, 3σ). This work demonstrates the feasibility of dry development for sub-10 nm EUV patterning, providing an alternative to overcome the fundamental limits of wet development.

키워드