Increasing plasma etch resistance of resists using fullerene additives

We utilize a new class of additive, Fullerenes, which appear to impart superior plasma etch resistance to resist films compared to other additives reported in the literature. [R. R. Kunz, S. C. Palmateer, A. R. Forte, R. D. Allen, G. M. Wallraff, R. A. DiPietro, and D. C. Hofer, Proc. SPIE 2724, 365 (1996).] The plasma etch resistance of PMMA impregnated with [60]Fullerenes was compared directly to pure PMMA; adamantane-and 1-chloroadamantane-impregnated PMMA; the novolac-based, e-beam/x-ray photoresist SAL 605 (The Shipley Co.); APEX-E (IBM Corp.); and an experimental, 193 nm resist, XP96545-7A (The Shipley Co.). These comparison experiments were done under CF4 and Cl-2 reactive ion etch conditions. The plasma etch rate of PMMA decreased linearly with concentration of [60]Fullerenes in the film up to at least 11 wt %. When 10.8 wt % C-60 (approximate to 7.3 vol %) versus total solids were added to PMMA, the etch rate ratio to SAL 605 dropped from 1.80 to 1.38 in CF4 and from 2.5 to 1.55 in Cl-2. Improvements in etch resistance with Fullerenes added to PMMA were similar for both Cl-2 plasmas and CF4 plasmas, which was contrary to the results of the unmodified XP96545-7A resist and that reported for alicyclic additives, [R. R. Kunz, S. C. Palmateer, A. R. Forte, R. D. Allen, G. M. Wallraff, R. A. DiPietro, and D. C. Hofer, Proc. SPIE 2724, 365 (1996)]. [60]Fullerenes were also successful at improving the plasma etch durability of pure polystyrene films, showing that these additives have the potential to improve etch resistance of films to better than novolac, provided solubility limitations can be overcome. The absorptivity of [60]Fullerenes at 193 nm can be reduced by derivatizing the C-60 to C60H36, C60F40, or C60F48. The fluorinated Fullerenes show high solubility in propylene glycol methyl ether acetate and 1-methoxy-2-propanol. On a mole basis, fluorinated Fullerenes improve the etch resistance of PMMA as well as [60]Fullerenes showing the potential of derivatized Fullerenes for various photoresist applications, including 193 nm imaging materials. (C) 1997 American Vacuum Society.