Study of damage mechanism and hardening method of chemical amplified resist by charged particle from plasma etching

Extreme ultraviolet (EUV) lithography offers the advantage of achieving finer patterns by using a wavelength of 13.5nm. However, due to the high energy and low density of photons of the EUV light, the EUV-sensitive photoresist has been thinner than conventional deep ultraviolet (DUV) resist. In addition, the thin thickness of EUV resist after pattern formation, it could be easily damaged by plasma during the plasma etching process to transfer the pattern to hardmask, resulting in higher line edge roughness (LER) and line width roughness (LWR). In this study, we investigated the etching characteristics of negative-type CAR during the reactive ion beam etching (IBE) of hardmask materials (Si₃N₄ and SiO₂) using CF₄ + Ar gas mixture. The results are compared with those from the neutral beam etching (NBE) process. Also, we proposed the hardening method that can minimize the radiation damage, and its effect was demonstrated. When NBE was used, the etch selectivity between materials such as SiO₂, Si₃N₄, and PR was higher than IBE. Also, the changes in LER and CD after NBE were three and two times lower, respectively, compared to IBE, and significant differences in RMS surface roughness values were observed between IBE and NBE. From these results, PR undergoes more damage from IBE. In order to minimize the damage of EUV PR, the application of CS2 plasma treatment resulted in a significant reduction in ΔLER and ΔCD after IBE compared to before hardening.