Yasunori Uetani

Design of fulleropyrrolidine derivatives as an acceptor molecule in a thin layer organic solar cell

A systematic study on the design of fulleropyrrolidine derivatives as the acceptor of photovoltaic cells has been carried out using poly(3-hexylthiophene) (P3HT) as the model base polymer. It was found that N-methoxyethoxyethyl-2-(2-methoxyphenyl)fulleropyrrolidine worked as a good acceptor partner with P3HT and a high power conversion efficiency (PCE) (3.44%) was obtained; this is superior to that of the P3HT polymer including methyl [6,6]-phenyl-C61-butylate ([C60]-PCBM) under the same experimental conditions.

Design concept for a high‐performance positive photoresist

An attempt was made to design a high‐performance positive photoresist from the standpoint of the image formation process. There are a lot of trade‐off relationships among performance of a positive photoresist. A study was made to raise performance without the decrease in other performances. It was necessary to design a new type of novolak resin that has a molecular structure different from the existing materials. Many kinds of cresol–formaldehyde type novolak resins were synthesized and evaluated lithographically. Such items as molecular weight, molecular weight distribution, isomeric structure of cresol, the position of methylene bond, and the content of quinonediazide in a positive photoresist were investigated. Three methods were found useful: (i) to apply high‐ortho novolak resins that have a high content of ortho–ortho’ methylene bonds (ii) to optimize molecular weight distribution of novolak resins, and (iii) to optimize the content of quinonediazides in a photoresist. These results are explained in...

Standard developer available ArF resist and performance

Alicyclic groups are preferable resin components of ArF resists due to better dry-etching resistance and higher transparency at 193 nm. On the other hand, Alicyclic groups bring poor adhesion of ArF resists during wet development, because of their higher hydrophobic nature. To avoid the peeling problem diluted developer has been suggested to use. However, the compatibility with existing standard developer of i-line and KrF resists is necessary for the mass production. In this paper we compared two kinds of resists for the standard developer (TMAH 2.38%) application. The former has AdCEE unit and norbornene derivative/maleic anhydride alternating copolymer, together with relatively weak organic acid generating PAG. The latter having 2MAdMA/GBLMA copolymer and onium salt PAG shows better lithographic performance.

Positive ArF resist with 2EAdMA/GBLMA resin system

We compared 2MAdMA(2-Metyl-2- Adamantylmethacrylate)/GBLMA((gamma) -butyrolactone methacrylate) resin system and 2EAdMA(2-Etyl-2- Adamantylmethacrylate)/GBLMA resin system. 2EAdMA/GBLMA resin system showed higher sensitivity, dissolution contrast and better adhesion to silicon substrate than 2MAdMA/GBLMA resin system. These results shows that 2EAdMA/GBLMA resin system is suitable for practical ArF positive resist.

Investigation of cyclopolymerization for ArF positive photoresist

Cyclopolymerization methodology is unique because it uses a standard free radical polymerization that is free from the use of metal catalyzed chemistry while it still can provide the main chain cyclic structure. The feasibility and applicability have been examined previously, from which some of the potential opportunities have been revealed. Our initial research direction was aimed at developing robust etching resistant acrylic resins through cyclopolymerization. During the course of our investigation it came to our attention that there might be more than one benefit we could get from this approach and here in reported is our recent progress in the study. A series of diacrylic monomers and their cyclic polymers have been prepared and evaluated for ArF optical lithography applications. The reaction of acrylic esters that have essential functional groups for lithographic performances such as an acid-cleavable bulky adamantyl group and a polar lactone group with formaldehyde in the presence of diazabicyclo-(2,2,2)octane has been shown to provide access to an ether linked symmetric or asymmetric diacrylic monomer depending on the starting materials with a reasonable yield after an adequate purification procedure. While the main research focus of cyclopolymerization of diacrylic monomers has been an improvement of dry etching resistance, an equal interest was placed on enhancing homogeneity in the polymerization reaction medium.

Modification of 193-nm (ArF) photoresists by electron beam stabilization

For the sub 130nm technology nodes, 193nm(ArF) lithography has become the technology path of choice. Similar to the 248nm technology set, the resist systems being used for 193nm lithography are based on chemical amplification to achieve high throughput at the low exposure energy at 193nm. The current ArF resist systems have experienced problems with etch selectivity and line slimming during CD-SEM measurement. Both of these issues are related to the resist platform and constituents used to achieve the desired lithographic performance. This investigation evaluates electron beam stabilization as a way of addressing both the etch selectivity and line slimming issues associated with some of the current 193nm resist systems. Varying levels of electron beam dose were evaluated in an attempt to understand the effects of energetic electrons on ArF resist materials. Chemical changes in the resist were monitored for blanket resist films by FTIR, film shrinkage, and changes in index of refraction, all as a function of dose level. An increase in modification of the resist is seen with increasing dose. Blanket resist etch rate studies were performed as a function of stabilization condition. The etch rate of the resist was found to decrease with increasing dose as compared to untreated resist. Correlation of the chemical changes and etch rate reductions are proposed for the resists considered. The CD changes induced by the electron beam stabilization were monitored as a function of dose applied. Minimal CD change was seen as a result of the stabilization process. The impact of the electron beam process on line slimming was evaluated by performing repeated measurements on resist features with different levels of electron beam dose. The line slimming was found to be significantly reduced for the higher dose levels considered. Etch selectivity was evaluated by cross-section SEM measurements after etch of features with different levels of stabilization. An increase in the etch selectivity and pattern stability were observed with increasing stabilization dose.

Effect of fluorinated monomer unit introduction to KrF resin system in F2 lithography

We reported the novel copolymer system containing fluorine atom with hydroxystyrene (HST) and 3-(perfluoro-3- methylbutyl)-2-hydroxypropyl methacrylate (MBHPMA). Using the copolymer, melamine crosslinker and PAG, negative resist was formulated. Transmittance of the resist film was 35% at 0.1micrometers thickness. High contrast negative pattern was obtained by F2 excimer laser exposure. Dry-etching resistance of the resist was comparative to novolak type i- line resist.

Effects of Anisotropic Excitation in Laser-Induced Fluoresceruce Spectroscopy (LIFS)

Various features of the effect of alignment in the upper-level population on the observed emission-line intensity, i.e., the spatially-anisotropic intensity distribution and polarization, are demonstrated using laser-induced fluorescence spectroscopy on the neon 2p53s-2p53p transitions in a plasma. Disalignment by atomic collision is observed on the 2p2 level, and its rate coefficient is determined as (1.70 ±0.03) ×10-10 cm3s-1. The case of hyperfine-structure lines is discussed. Polarization is observed in the hydrogen Balmer α line fluorescence following the laser excitation of the same transition. Conditions are given under which the alignment effect is eliminated or can be neglected. Cases of unpolarized-light excitation and high-intensity excitation are discussed.

Comparison of acrylate and methacrylate resin system in ArF lithography

Using 2MAdMA(2-Metyl-2-Adamantylmethacrylate), 2MAdAA(2-Metyl- 2-Adamantylacrylate), GBLMA((gamma) -butyrolactone methacrylate), GBLAA((gamma) -butyrolactone acrylate) monomers, 4 types of copolymers, 2MAdMA/GBLMA, 2MAdMA/GBLAA, 2MAdAA/GBLMA, 2MAdAA/GBLAA resins were prepared. The same PAG formulation was applied to these resins to make ArF resist samples. Resolution capability, dry-etching resistance were evaluated. From the result, it can be concluded that 2MAdAA/GBLMA resin system has the best balance in dry etching resistance, resolution and sensitivity.

Synthesis, Properties, and Photovoltaic Performance of Copolymers Based on Difluorodioxocyclopentene-Annelated Thiophene

New π-conjugated polymers containing difluorodioxocyclopentene-annelated thiophenes as an electron-accepting unit have been synthesized for application to p-type organic semiconducting materials in organic photovoltaics. The photophysical and electrochemical properties of these polymers were investigated by UV–vis absorption spectra and cyclic voltammetry measurements. The carrier mobility measurement of the copolymer on organic field-effect transistor devices revealed p-channel behavior. Bulk heterojunction photovoltaic devices made from blends of the polymer and [6,6]-phenyl-C71-butyric acid methyl ester showed moderate photovoltaic characteristics with a power conversion efficiency of 0.77%.