Naomi Shida

Highly transparent chemically amplified ArF excimer laser resists by absorption band shift for 193 nm wavelength

Naphthalene-containing chemically amplified resists for ArF excimer laser exposure are proposed, based on the concept of the absorption band shift by conjugation extension. Newly developed ArF excimer resists show a high transparency at 193 nm wavelength, a high sensitivity and a high contrast. The sensitivity of the resist is 150 mJ/cm2, which is 20 times greater than that of poly(methylmethacrylate) (PMMA). Furthermore, a 0.16 µ m pattern could be successfully fabricated by an ArF excimer laser stepper with 0.55 numerical aperture (NA) projection lens.

Device Simulator for Designing High-Efficiency Light-Emitting Diodes

A general device simulator has been constructed for designing high-efficiency light-emitting diodes (LEDs). The optical characteristics, including the spatial profiles of the light extracted from LEDs, are important for practical LED applications such as display and illumination. The radiation patterns are affected by device structures such as electrodes, which determine the current distribution, and by the light-absorbing layers, which intercept the internal light emission. The simulator analyzes light extraction efficiency and the radiation pattern, both of which are very important in designing an optical system using LEDs. The simulator is useful for designing high-efficiency LEDs and package configurations for various applications.

Advanced materials for 193-nm resists

Acrylate monomers containing alicyclic side chains featuring a series of polar substituent groups were assumed to be model compounds. Solubility parameters were calculated for the corresponding acrylate polymers. These acrylate monomers were synthesized using a novel aerobic oxidation reaction employing N-hydroxyphtalimide (NHPI) as a catalyst, and then polymerized. These reactions were confirmed to be applicable for the mass-production of those compounds. The calculation results agreed with the hydrophilic parameters measured experimentally. Moreover, the relationship between the resist performance and the above-mentioned solubility parameter has been studied. As a result, a correlation between the resist performance and the calculated solubility parameter was observed. Finally, resolution of 0.13-micron patterns, based on the 1G DRAM design rule, could be successfully fabricated by optimizing the solubility parameter and the resist composition.

Chemically amplified ArF resists based on cleavable alicyclic group and the absorption band shift method

Recent advances in the single-layer resist for forming finer patterns have led us to a search for new resist materials for the ArF excimer laser. We describe a novel, environmentally friendly, single-layer resist based on a menthyl acrylate copolymer protected with a cleavable alicyclic group and the absorption band shift method.

Chemically ampilified ArF excimer laser resists using the absorption band shift method

The VUV-absorption spectrum of aromatic compounds can be red-shifted toward longer wavelengths to make the window of absorption align with 193 nm by extending the conjugation length of the double bonds. Based on this observation, the new concept of absorption band shifting is proposed as a way to increase the transparency of resist components for 193 nm ArF excimer laser exposure. A chemically amplified single-layer ArF excimer laser resist consisting of naphthalene-containing photoacid generator, a dissolution inhibitor, and base polymer has been newly developed. Using this resist, a 0.17 micrometers line/space pattern with a vertical resist profile was resolved by a prototype 0.55 NA projection lens for ArF excimer laser exposure, and a resolution limit of 0.16 micrometers was achieved.

Chemically amplified resists using the absorption band shift method in conjunction with alicyclic compounds for ArF excimer laser lithography

The resist comprising naphthalene rings instead of benzene rings was developed for ArF excimer laser lithography. Naphthalene shows outstanding dry etch resistance, stronger adhesion to silicon surface and low hydrophobicity compared with most alicyclic compounds. Di-tert-butyl 2-[(1- adamanthyl) carbonylmethyl] (ADTB) was developed as an additive to improve the characteristics of development of base polymer. Although ADTB has tert-butyl protective groups, the decomposition temperature is low compared with that of polymer which has a tert-butyl protective group. Moreover, the dry etch resistance of the resist becomes greater as ADTB content increases. 0.133 micrometers L/S patterns were fabricated using Nikons ArF prototype exposure system. Next, in order to improve the adhesion of the resist having the alicyclic frame, introduction of naphthalene in to the resist was attempted. The new resists which has naphthalene frame showed stronger adhesion and 0.15 micrometers L/S patterns were fabricated using the ArF exposure system with the standard developer.

193-nm single-layer resists based on advanced materials

Recent advances in the 193-nm single-layer resist for forming finer patterns have led us to search for new resist materials for the ArF excimer laser. We describe novel, mass productive single layer resist based on hybrid hyper lactonic polymer which has high resolution, good hydrophilicity, and dry etch resistance. Further, we investigate the lactonic polymer, which has Mass-productive Ultimate Norbornyl group with Outstanding Solubility (MUNGOS).

Dissolution inhibitors for 193-nm chemically amplified resists

Dissolution characteristics and adhesion of 193-nm resists have been investigated by using molecular orbital calculations. The calculation indicated that naphthalene compound had better adhesion than alicyclic compounds by a factor of 1.2. Another calculation result obtained indicated that naphthalene was more hydrophilic than alicyclic compounds. In order to improve the adhesion and dissolution characteristics of the alicyclic resist, introduction of the naphthalene backbone into alicyclic resists was attempted in the form of additives (dissolution inhibitors) or copolymer components. Dissolution inhibitors that have simultaneously a naphthol novolak backbone and a characteristic generate carboxylic acid, such as tetrahydropyranyl ester of naphthol novolak compound condenced with glyoxlic acid (NV4THP), were the most effective dissolution inhibitors increasing dry etch resistance of base polymer by 14% and pattern resolution of original resist by 10%. The naphthalene dissolution inhibitor also largely improves pattern adhesion. These results were consistent with above-mentioned calculation results. 193-nm resists containing vinyl naphthalene in the copolymer structure were also investigated and fundamental resist requirements were satisfied with this polymer by adding adamantane dissolution inhibitor di-tert-butyl 2-((1-adamanthyl)carbonylmethyl) malonate (ADTB).

Comparision between alicyclic resist platforms in advanced 193-nm and 157-nm lithography

Alicyclic resist platforms have already thought to be imperative in 70-110 nm nodes advanced optical nano-lithography using ArF (193-nm) or F/sub 2/ (157-nm) excimer laser exposure system. In this paper, comparative studies of physical and chemical properties of these alicyclic platforms were reported. We also attempted to clarify the essential difference of their potentials in advanced optical nano-lithography.