The novel polyimide having spiropyran groups on their side chain was synthesized, and the thin films of the polyimide on glass substrates were prepared. It was confirmed that the surface wettability of these films were changed from around 76° to around 67° by UV (365 nm) light irradiation, and the surface wettability were reversibly changed from 67° to 76° by Vis (visible) light irradiation. These wettability changes were photo-cyclized three times. The UV-Vis spectroscopy analysis indicates that the photo-induced isomerization of the spiropyran group leads to reversible changes on the surface of the polyimide films.

View full abstract

Polymer membranes with high gas permeability have been strongly desired for energy- and environmental-applications. In this study, novel mixed matrix membranes (MMMs) composed of fluorinated polyimide and silica nanoparticles modified with various organic moieties were fabricated, and their gas permeation properties were evaluated. The influence of surface-modification structures, especially the length and density of linker molecules, on gas permeation properties of the MMMs were investigated. The modification structures affected the formation of high CO₂ permeable space on the nanoparticle surface, and appropriate structures effectively enhanced the CO₂ permeability of the MMMs.

View full abstract

Pressure-induced variations in refractive indices and acoustic velocities of a spin-coated aromatic polyimide (PI) film, poly(4,4’-oxidiphenylene pyromellitimide), were analyzed between atmospheric pressure (0.1 MPa) and 2 GPa by Brillouin scattering measurements with the symmetric platelet and the back scattering geometries for the film surface and the cross-sectional surface. At high pressures, anisotropies in acoustic velocity and refractive indices were clearly observed between the in-plane and out-of-plane directions. Additionally, the average refractive index of the PI film was estimated to increase from 1.682 to 1.80 by applying pressure up to 2 GPa due to the densification of aggregation structures of the PI film.

View full abstract

With the paradigm shift in the development and utilization of energy systems from petroleum to electricity owing to sustainability considerations, the development of high-performance electrical devices has become increasingly important. Insulating materials are one of the key technologies for the practical application of next-generation electric devices because they must be driven at higher voltages and their complex shapes cannot be coated using current techniques. Therefore, the development of insulating materials with thermostability and facile electrodeposition ability is crucial for the production of high-performance next-generation electric devices. In the current study, anionic electrodeposition coating was successfully performed using poly(amide acid) nanoparticles, which can be converted to polyimides upon thermal annealing. Hybrid coating using polyimide/bentonite with an inorganic filler content of 40% was also performed, and the resulting electrodeposition films were thermostable to more than 450 °C.

View full abstract

Reaction development patterning (RDP) applicable to polyacetals was investigated by using inverse acid-base condition, namely, photo-base generator and acidic developers. Polyacetal films composed of polyacetals, O-phenylacetyl 2-acetonaphthone oxime as a photo-base generator and benzophenone as a photosensitizer gave positive-tone patterns after irradiation with an ultrahigh-pressure mercury lamp and successive dipping in developer containing carboxylic acid, methanesulfonic acid or sulfuric acid. Reduction in thickness at the unexposed area was inhibited by incorporation of trifluoromethyl groups to polyacetals.

View full abstract

A facile approach for the synthesis of an n-type π-conjugated hyperbranched polymer, namely hyperbranched polypyridinebenzene, is proposed based on the copolymerization of 1,3,5-tribromobenzene (BeBr₃) and 2,5-dibromopyridine via chain-growth condensation polymerization catalyzed by Ni(dppp)Cl₂. The use of BeBr₃ as a branching unit simplifies the synthesis of n-type Π-conjugated hyperbranched polymers, compared with a similar hyperbranched polymer prepared from 2,4,6-tribromopyridine (PyBr₃) and 2,5-dibromopyridine requiring a lengthy synthetic route to give the starting material PyBr₃. The results of UV-Vis spectroscopy and cyclic voltammetry suggest that our synthesized polymer retains its hyperbranched structure, which is beneficial in electrochemical doping.

View full abstract

Semiconductor packages with redistribution layers have been necessary with their miniaturization and functionalization. Dielectric materials for the packages require low-temperature curability to avoid thermal damage of devices and thermally unstable materials in the packages, and to keep high reliability for various thermal tests. Low-temperature curable positive-tone photosensitive material AR-5100 was developed and its reliabilities were evaluated. AR-5100 kept mechanical properties after reliability tests. Especially, AR-5100 had good bias HAST tolerance. AR-5100 is capable of adapting to next-generation packages which require high reliability.

View full abstract

We successfully developed redistribution structure by using photosensitive polyimide and all wet Cu plating processes. To obtain the structure, patterned Cu was obtained by non-electrical plating on photosensitive polyimide layer with a mask of photo-resist. Various types of surface treatments on polyimide layer were investigated to obtain good adhesion between Cu and polyimide. In this work, we coated the photosensitive polyimide by a slit coater and found a suitable wet surface treatment to obtain good adhesion to plated Cu. The all wet Cu processes are composed of wet activation process and electro-Cu plating process. By combining all these processes, 40μm line and space Cu pattern was obtained by using a 500-600 mm glass panel. In addition, 2μm line and space Cu pattern was obtained on an 8 inch glass wafer.

View full abstract

Elucidation of interfacial charge separation and recombination mechanisms is crucial to improve performance of organic-inorganic metal halide perovskite solar cells. Here, we have investigated influence of initially populated electron and hole potential levels in a perovskite conduction band (CB) and valence band (VB), respectively, by altering an excitation wavelength on interfacial charge separation and recombination dynamics in a CH₃NH₃PbI₃ perovskite film sandwiched by a mesoporous TiO₂ structure as an electron transport material (ETM) and a spiro-OMeTAD film as a hole transport material (HTM). Multi-phasic electron injection reactions are observed over <1.2 to several tens of nanoseconds, while most of holes are injected to a spiro-OMeTAD layer within the transient emission spectroscopy instrument response time (1.2 ns). In contrast, interfacial charge recombination rates are slower (from 5 ms to 1.3 s) with the increase of the excitation wavelength. These kinetics suggest that as long as low excitation intensity is employed, e.g. 10 nJ/cm² or 1 sun (100 mW/cm²), the APCE of ~100% can be expected at any excitation wavelength for the solar cells based on FTO/c-TiO₂/m-TiO₂/MAPbI₃/OMeTAD films.

View full abstract

Oxime derivatives, having a N-O bond in the molecule structure, are excellent photo reactive compounds. Oxime type photoacid generaters with adamantyl and perfluoroalkylsulfonyloxy groups and without aromatic groups were prepared, and their absorption spectra and thermal properties were measured. The compounds designed with photoacid generator in deep ultraviolet (DUV) region have good transparency in the region. The thermal stability of these PAGs depended on the chain length of acid precursor groups. The quantum yields of acid generation were substantially high. These aliphatic oxime sulfonates can be expected to be PAGs in DUV.

View full abstract

Random or block copolymers that include the tert-butyl ester may be used to generate nanocelluar foams. In this paper, we demonstrated the synthesis of asymmetric PS-b-PtBMA using the organotellurium mediated radical polymerization (TERP). The TERP is suitable for block copolymer synthesis with precise control of the molecular weight (M_n) while having low dispersity (D). Our results show that for M_n = 23.75 kg/mol, relatively low dispersity D = 1.18 has been achieved with 87% degree of livingness after the PS polymerization. However, at M_n > ~50 kg/mol, D was largely increased due to the high viscosity of the polymer solution at high conversions.

View full abstract

Although in the last year the development of extreme ultraviolet (EUV) lithography has allowed to push the lithographic performance of the EUV photoresists, the high-volume-manufacturing (HVM) requirement to have a cost-effective low exposure dose photoresist (<20 mJ/cm²) remains a big challenge and patterning stochastic defectivity at nano-scale currently still is the major limiting factor of the lithographic process window of EUV resist when looking at tight pitches below 40 nm. To get a better understanding of stochastic patterning failures for such tight pitches it is crucial to quantify them already at the early stage of R&D resist screening phase. In this work we describe a new way of looking at the performance of EUV photoresists. We present the EUV resist nano-failure characterization results when printing dense line-space pattern logic use case on the ASML NXE3300 full field EUV scanner. We analyze through dense pitches three chemically amplified resists with different sensitivity, we quantify the nano-bridges and we discuss potential root causes from photon-shot-noise, imaging and material standpoint.

View full abstract

Two processes, the PVA (polyvinyl alcohol) /PET (polyethylene terephthalate) bilayer-film process and the delayed UV cure resin process, are proposed in order to improve the transfer printing process for multilayer structure fabrication. In the PVA/PET bilayer-film process, a commercial PVA/PET bilayer-film is used. The water soluble PVA pattern is used as the temporal mold for the PMMA pattern fabrication. Since the PVA temporal mold is dissolved in water, the demolding process, which often becomes serious issue for the transfer printing, can be eliminated. Although two layer structure by stacking PMMA films with 2 μm half pitch LS pattern can be fabricated by the thermal press bonding, the press conditions for the successful transfer is restricted. The delayed UV cure resin process is developed instead of the thermal press bonding. The delayed UV cure resin is used as the adhesive layer for the press bonding. Since its UV cure gradually proceeds after UV exposure, the press bonding can be started after the UV exposure. Two layer structure by stacking PMMA films with 2 μm half pitch LS pattern can be successfully fabricated by combination of the PVA/PET bilayer-film process and the delayed UV cure resin process.

View full abstract

Investigations on the resist film depth-profile of a Zr-based EUV metal resist (which contains methacrylic acid or MAA as shell) reveal that the metal cores (Zr) are homogeneously distributed across the film-depth. However, the shell molecules (MAA) in the same resist film have an inhomogeneous distribution (relatively high concentration at the film surface compared to the film bottom). In addition, the total concentration of shell molecules across the film depth is significantly affected (decreases) due to post coating delay and increased exposure dose. Moreover, it is confirmed that the existence of such metal resist film depth inhomogeneities affects the resist’s dissolution properties in the developer solution. Specifically, variations in metal resist dissolution characteristics between the film surface, mid-film, and the film bottom are observed. These results confirm the impact of metal resist film properties on its solubility in the developer solution, which can directly affect patterning performance (resolution, line edge/width roughness (LER/LWR), and sensitivity), especially LER/LWR.

View full abstract