The relationship between photoacid generator (PAG) structures, using N-sulfonlyoxy imide compounds, and their resist performance were investigated from the viewpoints of the efficiency of acid generation and the behavior of generated acid diffusion. The acid generation efficiency was monitored by the use of acid sensitive dye. The increase in the absorption coefficient of N-sulfonlyoxy imide at 248nm based on imide parts, rather than sulfonate parts, resulted in the increase of the efficiency, and then giving the higher photo speed on resist. In order to estimate the magnitude of the generated acid diffusion in resist film, the catalytic chain length, that is the turnover value, of the acid catalyzed t-BOC decomposition were determined. The turnover was decreased with the increase of the steric hindrance by altering the substituents of generated sulfonic acid, thereby lowering the photo speed, while improving the resist resolution. From these tendency, the control of the acid generation efficiency and the generated acid diffusion in resist film were influential to determine the resist performance. Furthermore, the product analysis on the photolysis of N-sulfonlyoxy imide compound, together with the calculation of the molecular orbital and the estimation of their interaction with poly(p-hydroxystyrene) (PHS), were carried out for a better understanding of the structural dependency. On the basis of the knowledge, the photolysis mechanism of N-sulfonlyoxy imide compound was proposed.

The relationship between the higher structure of resist polymers, such as novolak (NVK) and poly(hydroxystyrene) (PHS), and their alkali dissolution and dissolution inhibition characteristics were investigated. From the calculations of the polymers with molecular mechanics (MM) and molecular dynamics (MD), NVK exhibited the structure with intramolecular hydrogen bondings through ortho-ortho methylene bonds, while PHS formed them through the OH group on ortho position, thereby both giving oriented structures with OH groups in the molecular interior. The alkali dissolution of the polymers having such higher structures showed lower values, and these tendency corresponded to the interpretation of percolation mechanism with respect to the alkali dissolution of polymers. In order to estimate the higher structures of the polymers, the n values in the Henderson-Hasselbach equation were measured. The increase in the n values resulted in the decrease in the alkali dissolution of the polymers. Furthermore, the structural factors of dissolution inhibitors on chemical amplification resist were also studied for their inhibition characteristics. The acid decomposition of inhibitors were stepwise proceeded resulting in that the dissolution inhibitors significantly lost their inhibition ability at a certain step in decomposition. With selective use of this step, the dissolution discrimination of the resist could be improved.

It is generally believed that the chemically amplified reaction between photo-generated acid catalyst and acid labile group of polymer during post-exposure bake (PEB) process plays a critical role for the reduction of line width roughness (LWR) in ArF lithography. In this work, we revealed experimentally how large the chemically amplified reaction affects LWR, and developed a new resist system with low LWR. Aerial image contrast dependence on LWR revealed that the innate LWR in a conventional ArF photoresist, which is independent of the aerial image contrast, was 5 nm. Surface roughness of a non-patterned resist film at half-exposed area, which was well correlated with LWR, was measured by AFM. The surface roughness increased from 1.7 nm to 10.8 nm during PEB process. The half-exposed area was baked and again dissolved into organic solution, and spin-coated on Si wafer, and then developed with 2.38 % TMAH solution. The recoated half-exposed resist film caused a 60 % reduction on the surface roughness. It revealed that uniform distribution of deblocked polymer was important factor for roughness reduction. HPLC analysis indicated that distribution of acidic group formulation in the polymer was gradually extended with increasing exposure dose. A Resist system that suppresses the chemically amplified reaction successfully reduced LWR from 6.5 nm to 4.8 nm.

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