Development of partially fluorinated EUV-resist polymers for LER and sensitivity improvement

In order to improve EUVL resist characteristics, especially sensitivity, we have investigated two types of partially fluorinated resist polymers. The one was side chain fluorinated PHS type resist polymers. The other was main chain fluorinated resist polymers. Poly (p-hydroxystyrene) (PHS) type polymers with trifluorostyrene (TFSt) were synthesized and characterized their sensitivity behavior. From this evaluation, we found that PHS contained TFSt unit had a high sensitivity, keeping their etching durability. We expect that TFSt unit can work to enhance the resist sensitivity in PHS based EUVL resist polymers. Main chain fluorinated polymers based FIT unit (FITMAd and FITAdOM) were synthesized. FITMAd and FITAdOM showed high sensitivity compared to non fluorinated reference sample. From molecular weight measurement, we infer that the polymer main chain of FITMAd can be decomposed by irradiating with EUV light. The outgassing of FITMAd and FITAdoM were measured. There is no big difference between the total outgassing of FIT polymers and that of non fluorinated acrylic sample. And small amount of Hydrogen fluoride (HF) were detected. We infer that FITMAd and FITAdOM are decomposed then HF is generated under EUV exposure. From these results, we expect that FIT unit can work to enhance the resist sensitivity and can act main chain decomposed resist unit in EUVL resist polymers.