ArF immersion lithography using water as a fluid medium enables production of 45 nm features. Extending immersion lithography to 32 nm or below requires increases in the refractive indices of the lens material, the immersion fluid, and the resist material. However, a material with a high refractive index generally also has high absorbance. In attempt to design a resist with high refractive index and low absorbance, we studied several types of sulfur-containing polymers and determined which sulfur groups increase the refractive index without increasing the absorbance at 193 nm. We describe new thioester and sulfone structures that enable high index with low absorbance. This chemistry has been exploited to produce polymers with a refractive index of 1.8 at 193 nm and an absorbance less than 1.4 &mgr;m-1. The compatibility of the sulfur functionality with chemically amplified imaging chemistry was demonstrated by printing at 193 nm.
A new ArF matrix based on poly(vinylsulfonamide) has been developed. Sulfonamides, whose pKa values are comparable to those of phenols, can be used as acidic functional groups in the design of chemically amplified resist (CAR) and aqueous base developable resist. Various poly(N-alkyl vinylsulfonamide)s were prepared (R=H, CH2CF3, Pr, 1-adanmantyl), and showed high transparency at round 193 nm region. Depending on the substituents, the dissolution rates of films in a 2.38 wt% aqueous tetraethylammonium hydroxide solution were varied from 500 to 0.0035 nm/s. The tetrahydropyranyl (THP) protected poly(vinylsulfonamide) was prepared and the deprotection of THP was easily occurred when the photoresist containing a photoacid generator was exposed to UV light, followed by post-exposure baking.
We have investigated the possibility of amorphous low molecular weight polyphenols as a chemically amplified positive-tone electron-beam (EB) resist. Low molecular weight polyphenol, 4'4-methylenebis{2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)]methyl} phenol (3M6C-MBSA) as a base matrix, was protected by 1-ethoxyethyl (EE) groups to control the dissolution rate in 0.26 N tetramethylammonium hydroxide aq. developer. The film distribution in the depth direction for resist components with a Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and the Fourier amplitude spectra of line-edge roughness (LER) have been investigated to understand the relationship between them for the resists formulated with 3M6C-MBSA and two types of photo acid generator (PAG), triphenylsulfonium perfluoro-1-butanesulfonate (TPS-PFBS) and triphenylsulfonium n-octanesulfonate (TPS-nOS). From these results, it was found that the resist film consisting of TPS-nOS showed more homogeneous in the depth film distribution than that with TPS-PFBS, and the resist with TPS-nOS also indicated the suppressed LER value of 5.1 nm in the wide frequency range. Therefore, the homogeneity of the resist film may affect the pattern LER.
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