Novel chemically amplified resists incorporating anionic photoacid generator functional groups for sub-50-nm half-pitch lithography

A series of chemically amplified resists based on polymers of 4-hydroxystyrene, 2-ethyl-2-adamantyl methacrylate and a monomer-bound anionic photoacid generator (PAG) were prepared and characterized. Specifically, the following PAGs were separately incorporated into the main-chain of the polymers: the isomers triphenylsulfonium salt 2-(methacryloxy)-4-trifluoromethyl benzenesulfonate and triphenylsulfonium salt 4-(methacryloxy)-2-trifluoromethyl benzenesulfonate (CF3 PAG); triphenylsulfonium salt 4-(methacryloxy)-3-nitro-benzenesulfonate (NO2 PAG); and triphenylsulfonium salt of 1,1,2-trifluorobutanesulfonate methacrylate (MTFB PAG). Triphenylsulfonium salt 4-(methacryloxy)-2,3,5,6-tetrafluorobenzenesulfonate (F4 PAG) was used as the reference PAG. The intrinsic lithography performance of these polymer-bound PAG resists showed sub-50-nm half-pitch resolution and < 5 nm LER (3 sigma) under 100 keV electron beam patterning. The relative sensitivity of these materials under 100 keV e-beam exposure was MTFB PAG >= F4 PAG > CF3 PAG > NO2 PAG. Resolved pattern sizes of 40 and 32.5 nm half-pitch were obtained for fluorinated PAGs (such as MTFB PAG and F4 PAG) bound polymer resists under EUV interference lithography. The surface roughness was inspected with AFM.