Several super-resolution photolithography techniques are investigated. In annular illumination, both the resolution and depth of focus (DOF) are enhanced most effectively when 0.6<σ<0.7, whether or not contrast enhancement techniques, such as pupil filters or edge-enhancing phase-shift masks (PSMs), are used. Various contrast enhancement techniques are investigated from the viewpoint of spatial frequency characteristics, since flat characteristics are required for good mask-to-image fidelity. We propose a new high-spatial-frequency enhancing filter for annular illumination system which meets this requirement. We also optimize edge-enhancing PSMs for use with annular illumination. It is shown that both methods can improve the resolution/DOF characteristics while maintaining good mask-to-image fidelity. A practical resolution analysis shows that 0.2 (0.3) µm patterns can be delineated with a DOF of ±0.6 (±0.75) µm, if a KrF (i-line) stepper with an NA0.5 lens and high-contrast resist materials are used, with few restrictions on the pattern layout.

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We have developed novel alicyclic polymers having monoacid ester structures by alcoholysis of non-conjugated cyclic diene and malefic anhydride copolymers. This polymer, named ALPHA, exhibited good solubility (10-50 nmisec) in 0.113% aqueous tetramethyl-ammonium hydroxide solution without swelling. Absorbance was around 0.6 pm""' at 193 nm. Dry-etching resistance for C12BC13 gas was the same as that of polyhydroxystyrene. A two-component resist system, consisting of 1-ethoxyethylprotected ALPHA polymer and onium salt, produced 0.20-pm line-and-space patterns using a KrF excimer laser stepper with a phase-shifting mask. Consequently, we believe ALPHA is suitable as a base polymer for ArF excimer laser resists.

X-ray lithography with a wet-silylated and dry-developed resist has been investigated in order to overcome pattern collapse during wet development and to delineate fine-pitch and high-aspect-ratio patterns. In addition, the applicability to sub-0.1 µ m patterning is discussed. Silylation solution consists of B[DMA]DS (bis(dimethylamino)dimethylsilane) or HMCTS (hexamethylcyclotrisilazane) as the silylating agent, MCA (methyl cellosolve acetate) as the diffusion promoter and a solvent xylene. Silylation characterization and determination of optimum composition of the silylation solution have been performed using Fourier transform infrared spectroscopy (FTIR) measurement. Using the optimal wet-silylation and dry-developed resist system, 0.15 µ m line-and-space patterns of 1 µ m-thick resist (aspect ratio=6.5) and 0.08 µ m line-and-space patterns of 0.5 µ m-thick resist (aspect ratio=6) can be successfully delineated.

Acid-catalyzed insolubilization reactions between novel amphiphilic alicyclic polymers (named ALPHA) and aliphatic carbinols have been investigated for aqueous basedevelopable ArF single-layer negative resist. The combination of an ALPHA polymer (PMBH-BHMTCD) and an aliphatic carbinol (1,4-dioxane-2,3-diol (DD)) exhibited the highest insolubilization reactivity. It was found that the resist composed of PMBH-BHMTCD, DD, and N-trifluoromethanesulfonyloxynaphthalimide showed high dissolution rate contrast. However, the obtained patterns showed swelling distortion in the sub-pm range. FT-IR spectrometry indicated that the dominant insolubilization reaction was the crosslinking induced by acid-catalyzed etheriflcation. It is concluded that the swelling distortion in the sub-pm range was due to remaining carboxyl groups in the exposed area.