Naoki Yasuda

Polymer thin films containing Eu(III) complex as lanthanide lasing medium

Direct evidence of lanthanide(III) lasing using Eu(III) complex in polymer thin films (threshold level <0.05 mJ) is reported. The thin film consists of polystyrene containing Eu(III) complexes based on two criteria: (1) Higher emission quantum yield of Eu(III) complexes, which increases the rs (energy density), and (2) faster radiation rate at large B (Einstein coefficient). The microcavity was constructed by coating a glass substrate with a film having a high refractive index. The film thickness was found to be 1.71 mm. The threshold level for laser transmission was found to be <0.05 mJ.

Advanced Micro-Lithography Process with Chemical Shrink Technology

We have developed an advanced micro-lithographic process for producing 0.1 µm contact holes (CH). A chemical shrink technology, resolution enhancement lithography assisted by chemical shrink (RELACS) utilizes the cross-linking reaction catalyzed by the acid component existing in a predefined resist pattern. This RELACS process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. We evaluated the dependency of CH shrinkage on resist formulation. Though the acetal type KrF positive resist (low activation energy system) can achieve around 0.1 µm CH after RELACS processing under the optimized condition, the acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of the RELACS process largely depends on the resist chemistry used as the underlying layer. The results of these studies are discussed in terms of the influence of the base polymer on shrinkage performance and tendency.

Novel Silicone Polymeric Material with High Thermal Stability for Optical Waveguides

The optical loss and refractive index controllability of a novel silicone ladder copolymer (polyvinylphenylsilsesquioxane: PVSQ) were studied with respect to the application of the copolymer to optoelectronic components. PVSQ copolymers were prepared from trichlorophenylsilane and trichloro (vinyl) silane in the various mol ratios. They had a ladder structure consisting of siloxane bonds as the main chain and phenyl groups or vinyl groups as the side chain. PVSQ demonstrated excellent transparency at the wavelengths used in optical communication, 0.6–1.7 µm. The optical losses of PVSQ with 5 mol% vinyl group content in the side chain, were 0.99 and 1.05 dB/cm at the wavelengths of 1.30 and 1.55 µm, respectively. The in-plane refractive index of the polymers at 0.65 µm could be controlled to between 1.558 and 1.466 by changing the contents of phenyl groups and vinyl groups in the side chain. The out-of-plane refractive index could also be controlled to between 1.562 and 1.466. The thermal decomposition temperature of PVSQ, defined as that at which 10% weight loss occurred in N2 atmosphere, decreased with increasing vinyl group content, but all still showed decomposition temperatures above 500°C, ensuring sufficient thermal stability for polymer waveguide applications. Furthermore, the correlation between the vinyl group content and the refractive indices of the PVSQ polymers were discussed based on results of the molecular orbital (MO) calculations. The MO calculations were found to be useful for qualitative estimation of the change in the refractive index of compounds with a systematic derivative structure, such as PVSQ polymers.

Advanced Micro-Lithography Process for i-line Lithography

In our previous paper [Jpn. J. Appl. Phys. 40 (2001) 419], we reported the development of an advanced micro-lithographic process for producing 0.1 ?m contact holes by KrF excimer laser (248 nm) lithography. This chemical shrinkage technology, called resolution enhancement lithography assisted by chemical shrink (RELACS), utilizes the cross-linking reaction catalyzed by the acid component remaining in a predefined resist pattern. We report herein the results of the application of RELACS to i-line (365 nm) lithography. The properties of RELACS for i-line lithography were very different from those for KrF lithography. This is due to the difference in chemical mechanism between i-line and KrF resists. The characteristics of the application of RELACS to i-line lithography were studied by conducting basic experiments on the addition of a photo-acid generator (PAG) to an i-line resist and investigating the property of the cross-linking reactions involved in the pre-doping of various acids to RELACS film. Finally, we optimized RELACS materials to match i-line resist and realized the fabrication of contact holes less than 0.2 ?m diameter by i-line lithography.

Advanced microlithography process with chemical shrink technology

Mitsubishi Electric Corporation (MELCO) has developed an advanced microlithographic process for producing 0.1 micrometer contact holes (CH). A chemical shrink technology, RELACSTM (Resolution Enhancement Lithography Assisted by Chemical Shrink), utilizes the crosslinking reaction catalyzed by the acid component existing in a predefined resist pattern. This RELACSTM process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. This paper examines the process parameters affecting shrinkage of CH size. We subsequently evaluated the dependency of CH shrinkage on resist formulation. We conducted investigations of shrink magnitude dependency on each process parameter. (1) Photoresist lithography process: CH size, exposure dose, post development bake temperature. (2) AZR R200 [a product of Clariant (Japan) K.K.] RELACSTM process: Soft bake temperature, film thickness, mixing bake temperature (diffusion bake temperature), etc. We found that the mixing bake condition (diffusion bake temperature) is one of most critical parameters to affect the amount of CH shrink. Additionally, the structural influence of photoacid generators on shrinkage performance was also investigated in both high and low activation energy resist systems. The shrinkage behavior by the photoacid generator of the resist is considered in terms of the structure (molecular volume) of the photogenerated acid and its acidity (pKa). The results of these studies are discussed in terms of base polymer influence on shrinkage performance and tendency. Process impact of the structure and acidity of the photogenerated acid is explored. Though the experimental acetal type KrF positive resist (low activation energy system) can achieve around 0.1 micrometer CH after RELACSTM processing under the optimized condition, the experimental acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of RELACSTM process largely depends on the resist chemistry used as the underlying layer. Further, shrinkage degree can be controlled by process optimization even for the high activation energy type photoresist.

53.1: Fabrication of CNT Emitter Array with Polymer Insulator

A new method of fabricating CNT emitter array using polymer insulator with low outgassing has been developed. A dry etching process without the damage on the CNT has been found and it proved to decrease the turn-on voltage. Better emission properties than conventional insulator has been obtained.

Fabrication of CNT field‐emitter array using a polymer insulator

— The fabrication process of a carbon-nanotube (CNT) field-emitter array (FEA) having a polymer insulator is reported. This polymer material is suitable for a large-sized FEA because of its coating property and thermal stability. These features contribute to the display-image uniformity, the tolerance to the thermal-sealing process, etc. A new method of forming via holes on the insulator instead of gate holes has been developed. The method uses a spin-wet-etching (SWE) technique instead of the typical reactive-ion-etching (RIE) method. The RIE method damages and contaminates the CNT at the end of the etching process. However, the SWE technique ensures fine gate hole configurations with little under-cut without any damage nor contamination. An FEA panel 1.5 in. on the diagonal was fabricated by using the method. The FEA showed good emission uniformity with proper surface treatment of the CNT.