Masamichi Morita

Surface properties of perfluoroalkylethyl acrylate/n-alkyl acrylate copolymers

Wetting behavior of perfluoroalkylethyl acrylate (FA)/n-alkyl acrylate (AA) copolymers with the various length of side chains of the AAs is discussed from a standpoint of surface molecular mobility. The copolymerization reactivity ratio indicates that these polymers are random copolymers. The surface properties were studied by measuring dynamic contact angle, static contact angle and freeze-dried X-ray photoelectron spectroscopy, and the bulk properties by wide-angle X-ray diffraction and differential scanning calorimetry. The advancing contact angles for water were independent of side-chain length of AAs and were almost constant at 120°. We have attributed this phenomenon to the orientation of perfluoroalkyl groups (Rf groups, CxF2x+1) in air, which is independent of side-chain length of AAs. On the contrary, the receding contact angles showed small values of about 45° when n numbers below 8 and increased when n numbers above 12. This can be explained as follows. High wettability during the receding process at the n numbers below 8 results from regression of Rf groups at the water–solid interface caused by minimization of the interface free energy. The low wettability during the receding process at the n numbers above 12 shows that Rf groups cannot regress due to its crystallization. This mechanism is also supported by other measurements.

Room-temperature nanoimprint lithography for crystalline poly(fluoroalkyl acrylate) thin films

A mold with a line pattern was imprinted onto a thin film of poly{2-(perfluorooctyl)ethyl acrylate} with long crystalline fluoroalkyl groups (PFA-C8), and the nanoimprinting characteristics of PFA-C8 thin films were investigated. It was revealed that nanostructures could be imprinted on PFA-C8 at room temperature because of the weak interaction among the fluoroalkyl groups in crystallites. The nanotextured PFA-C8 film with a line pattern exhibited anisotropic wetting behavior. The anisotropic wetting behavior was attributed to the difference between the energy barriers of wetting in the direction parallel and orthogonal to the lines. Fabricated nanostructures were stable for annealing below its melting point and were stable at room temperature (RT) for several months.

Condensation reactions of phenolic resins. 1. Kinetics and mechanisms of the base-catalyzed self-condensation of 2-hydroxymethylphenol

Abstract There are many discrepancies in the interpretations of the condensation of hydroxymethylphenols. Further investigation, reexamination of the kinetics in particular, is needed to clarify the reaction mechanisms. In this paper, the kinetic aspects of the base-catalyzed self-condensation of 2 hydroxymethylphenol (2-HMP) are discussed. The order of reaction was determined from the dependence of the initial rate of reaction on the initial concentration of 2-HMP. It was confirmed that the reaction is kinetically of genuine first-order. Consequently, any SN2 mechanisms must be ruled out. A quinone methide intermediate hypothesis seems to hold: the dependence of reaction rate on the NaOH/2-HMP molar ratio could be explained kinetically based on the hypothesis.

Interfacial properties and emulsification in systems of perfluoropolyether/non-fluorinated oil/partially fluorinated oligomeric and polymeric compounds

Abstract Interfacial properties and emulsification were studied in the systems perfluoropolyether (PFPE)/non-fluorinated oil (NFO)/partially fluorinated oligomeric or polymeric compounds (Rf-Rh). All the Rf-Rh compounds were synthesized. The polymeric Rf-Rh compounds were random and graft copolymers with 1 H ,1 H ,2 H ,2 H -heptadecafluorodecyl acrylate (17FA) repeating units introduced into a trunk polymer chain. The Rf-Rh compounds dissolved or dispersed in most NFOs, but did not dissolve in PFPE. They depressed interfacial tensions at PFPE-toluene interfaces, which were mainly used in this study, with an increase in their concentrations. The polymeric Rf-Rh compounds were effective emulsifying agents for the formation of macroemulsions. The graft copolymers permitted the formation of very stable emulsions w ith a droplet diameter of about 200 nm, in particular. No direct relationship was found between the depression of the interfacial tensions and the stability of the emulsions. However, low interfacial tensions and sterically stable protection of an adsorbed film served for the formation of small-sized emulsion droplets, which contributed to reduce the sedimentation due to the gravitational force.

Room-temperature fabrication of nanotexture in crystalline poly(fluoroalkyl acrylate) thin film

A mold with a several hundreds of nanometres line pattern was successfully imprinted onto poly(fluoroalkyl acrylate) film with long crystalline fluoroalkyl groups (PFA-C8) at room-temperature.

Fabrication and characterization of multi-component organosilane nanofilms

Multi-component micropatterned organosilane monolayers are fabricated on a Si-wafer substrate by stepwise site-specific vacuum ultraviolet (VUV)-ray photodecomposition and chemisorption. The introduction of different organosilane components is confirmed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopic and lateral force microscopic observations reveal that the line-widths of the micropatterned surface correspond to those of the photomask. Contact angle measurement reveals that the micropatterning of the surface functional groups influences the magnitudes of surface free energy. A line pattern with high wetting contrast shows anisotropic water condensing behavior. Also, the patterned surface is used for the site-specific polymerization and site-specific adsorption of microparticles.

Surface molecular aggregation structure and surface physicochemical properties of poly(fluoroalkyl acrylate) thin films

Effect of side chain length on the molecular aggregation states and surface properties of poly(fluoroalkyl acrylate)s [PFA-Cy, where y is fluoromethylene number in Rf group] thin films were systematically investigated. Spin-coated PFA-Cy thin films were characterized by static and dynamic contact angle measurements, X-ray photoelectron spectroscopy (XPS), and grazing- incidence X-ray diffraction (GIXD). The receding contact angles showed small values for PFA-Cy with short side chain (y≤6) and increased above y≥8. GIXD revealed that fluoroalkyl side chain of PFA-Cy with y≥8 was crystallized and formed ordered structures at the surface region as well as bulk one. These results suggest that water repellent mechanism of PFA-Cy can be attributed to the presence of highly ordered fluoroalkyl side chains at the outermost surfaces. The results of XPS in the dry and hydrated states and contact angle measurement in water support the mechanism of lowering contact angle for water by exposure of carbonyl group to the water interface through reorientation of short fluoroalkyl chains. The surface nanotextured PFA-C8 through imprinting of anodic aluminum oxide mold showed extremely high hydrophobicity as well as high oleophobicity.

High-sensitivity EUV resists based on fluorinated polymers

There is a growing interest in the fluorinization of resist materials in improving pattern formation efficiency for extreme ultraviolet (EUV) lithography. The increased polymer absorption coefficient obtained through this resist platform is expected to enhance acid production and in effect improve pattern formation efficiency. Our work over the past several years has shown that the main-chain fluorinated base resins realized by the co-polymerization of tetrafluoroethylene (TFE) and norbornene derivatives offer high dissolution rates. Based on this, a EUV resist which was prepared using the by the fluorinated polymers was investigated. Imaging evaluations, using the small field exposure tool (SFET by Canon / EUVA) with annular (σouter 0.7 / σinner 0.3) illumination conditions were performed. Relatively high sensitivity of 6.3mJ•cm-2 for half-pitch (hp) 45nm and satisfactory resolution limit of hp 40nm was achieved. At present, line width roughness (LWR) was measured at comparatively large values of more than 8.4nm at hp 45nm. This shows that further material and process optimizations may be necessary to improve its present lithographic capability. However, these initial results have shown the potential of fluorinated-polymer based platform as a possible solution for high sensitivity, high resolution and low LWR EUV resists. In this paper, we report recent results of high sensitivity of 5.1mJ•cm-2 for half-pitch (hp) 40nm, optimization of protecting groups and photo acid generators

Influence of α-methyl group on molecular aggregation structure and surface physicochemical properties of fluoroalkyl side chain polymers

Influence of α-methyl group on molecular aggregation states and surface physicochemical properties of poly(fluoroalkyl acrylate)s [PFA-Cy, where y is fluoromethylene number in Rf group] and poly(fluoroalkykl methacrylate)s [PFMA-Cy] thin films were systematically investigated. Spin-coated PFA-Cy and PFMA-Cy thin films were characterized by dynamic contact angle measurements and grazing-incidence wide-angle X-ray diffraction (GIWAXD) measurements. GIWAXD data revealed that fluoroalkyl side chains of PFA-Cy and PFMA-Cy with y≥8 formed regular structures in the surface region as well as bulk one. However, the degree of orientation and ordering of the Rf groups of PFMA-C8 thin films was low. Also, the receding contact angle (θr) of PFMA-C8 thin films was lower than that of PFA-C8 ones. By annealing treatment, the θr of PFMA-C8 was increased. These results suggest that the Rf groups of PFMA-C8 were disordered due to presence of the α-methyl group. The Rf groups became ordered to pack closely each other by annealing treatment, so that the water repellency was increased.

Fluorinated-Polymer Based High Sensitivity Extreme Ultraviolet Resists

There is a growing interest in the fluorinization of resist materials in improving pattern formation efficiency for extreme ultraviolet (EUV) lithography. The increased polymer absorption coefficient obtained through this resist platform is expected to enhance acid production and in effect improve pattern formation efficiency. Based on this, a EUV resist which was synthesized by co-polymerizing tetrafluoroethelyne (TFE) and functional norbornene derivative was investigated. Relatively high sensitivity of 6.3 mJcm-2 for half-pitch (hp) 45 nm and satisfactory resolution limit of hp 40 nm was achieved. However, at present, line width roughness (LWR) was measured at comparatively large values of more than 8.4 nm at hp 45 nm. Further material and process optimizations may be necessary to improve its present lithographic capability. However, these initial results have shown the potential of fluorinated-polymer based platform as a possible solution for high sensitivity, high resolution and low LWR EUV resists.