Effect of Cl<sub>2</sub> Radical on Dry Development\nof Spin-Coated Metal Oxide Resist

In this study, the effects of Cl<sub>2</sub> radicals\non dry development\nof spin-coated metal oxide resist (MOR) and changes in its surface\nbinding states were investigated to verify the mechanism of dry development.\nDry development characteristics of tin hydroxide (Tin OH), which is\none of the MOR candidates for next generation lithography, were investigated\nas functions of process time and temperature using a Cl<sub>2</sub> radicals source. Non-UV-exposed Tin OH film showed a linear etch\nrate (1.77 nm/min) from the initial thickness of ∼50 nm, while\nthe UV-exposed film showed slower etch behavior (1.46 nm/min) in addition\nto the increase of film thickness for up to 3 min during the Cl<sub>2</sub> radical dry development. UV-exposed photoresist (PR) contained\nmore oxygen (Sn–O bonding) in the film due to the removal of\nbutyl compounds from the clusters during the UV exposure process.\nTherefore, due to the lower reaction of chlorine radicals with Sn–O\nin the UV-exposed Tin OH than the other bindings, the non-UV-exposed\nPR was preferentially removed compared to the UV-exposed PR. As the\ntemperature decreases, the overall etch rate decreases, but the difference\nin etch rate between exposed and unexposed Tin OH becomes larger.\nFinally, at a substrate temperature of −20 °C, the non-UV-exposed\nTin OH with a thickness of 50 nm was completely removed, while ∼30\nnm thick PR remained for UV-exposed Tin OH. Eventually, a negative\ntone development was possible with Cl<sub>2</sub> radical plasma due\nto the difference in activation energy between the UV-exposed and\nnon-UV-exposed films. It is believed that dry development using Cl<sub>2</sub> radicals will be one of the most important process techniques\nfor next-generation patterning to remove problems such as pattern\nleaning, line edge roughness, residue, etc., caused by wet development.