Kieko Harada

Energy Quenching Effects on Dry-Etching Durability of Copolymers and Polymer Blends of Vinylnaphthalene or α-Methyl Styrene with Methyl Methacrylate

Durabilities for O2 reactive ion etching (O2RIE) were studied as a function of number-average molecular weight (Mn) of poly(methyl methacrylate) [PMMA], poly(α-methyl styrene) [PMSt] and poly(2-vinylnaphthalene) [PVN]. Etching rates were independent of the Mn and in the descending order of PMMA, PMSt and PVN. Dry-etching durability which was defined as the reciprocal of etching rate relative to PMMA, of PVN was higher than that of PMSt. 2-Vinylnaphthalene (VN) moiety was found to be more effective for enhancing dry-etching durability than α-methyl styrene (MSt). Dry etching durabilities of copolymers (PMMA-co-MSt, PMMA-co-VN) were equal to those of polymer blends (PMMA/PMSt, PMMA/PVN) of the same composition and larger than the values calculated from the constituent homopolymers assuming the wt% or vol% additivity as the estimated bombardment probability by ion and neutral active species.

Organic Bistable Memory Switching Phenomena in Squarylium-Dye Langmuir-Blodgett Films

We have investigated the relationship between the switching phenomena and H-like aggregates in squarylium-dye Langmuir-Blodgett (SQ LB) films. The current-voltage characteristics of SQ LB films sandwiched between the top gold electrode and the bottom aluminum electrode indicated conductance switching phenomena below the temperature of 100°C but not at 140°C. Current densities suddenly increased at switching voltages between 2 and 4 V. The switching voltage increased as the temperature increased between room temperature and 100°C. Current densities were 50–100 µA/cm2 in a low-impedance state (ON state). A high-impedance state (OFF state) can be recovered by applying a reverse bias, and therefore, these bistable devices are ideal for memory applications. The dependence of conductance switching phenomena and ultraviolet-visible absorption spectra on annealing temperatures was studied. The results revealed that conductance switching phenomena were caused by the presence of H-like aggregates in the SQ LB films.

Large Electric Conductance in the Interface Direction of Polar/Nonpolar Double-Layered Hetero-Langmuir-Blodgett Films

Aluminum, arachidic acid (C20) multilayered and/or 2-dodecyl-7,7,8,8-tetracyanoquinodimethane (C12TCNQ) multilayered Langmuir-Blodgett (LB) films, and aluminum were deposited successively on a substrate. The electric conductance in the interface direction of the upper-Al/C12TCNQ/C20/under-Al structure, upper-Al/C20/C12TCNQ structure, and other control structures was measured using the four-point probe method. The electric conductance in the interface direction of only the upper-Al/C12TCNQ/C20/under-Al structure with the number of deposited LB layers between 3 and 5 was 10 or 100 times larger than that of the control structures, including aluminum thin films.

Dry-Etching Durability of Copolymers and Polymer Blends of Vinylnaphthalene or α-Methylstyrene with Methyl Methacrylate

Dry-etching durabilities of poly(2-vinylnaphthalene-co-methyl methacrylate), the blend of poly(2-vinylnaphthalene) and poly(methyl methacrylate) [PMMA], and poly(α-methylstyrene-co-methyl methacrylate) films were studied as a function of vinylnaphthalene or α-methylstyrene content against four types of dry etching: 1) O2 plasma etching ( O2 PE), 2) O2 reactive ion etching ( O2 RIE), 3) Ar+ sputter etching (Ar SE), and 4) Ar ion beam etching (Ar IBE). Since the etching depth increased linearly with etching time the two-component polymer films were regarded to be etched uniformly without selected removal of aliphatic monomer units. Substantial enhacement of the durability was observed by incorporating or blending small amounts of aromatic moiety into PMMA for physical etching (Ar SE, Ar IBE) and physical/chemical etching ( O2 RIE) as well as chemical etching ( O2 PE). O2 RIE is a synergetic process involving both physical bombardment and chemical reaction.

Conductance switching phenomena and H-like aggregates in squarylium-dye Langmuir-Blodgett films

The current–voltage characteristics of sandwich devices with the structure of top gold electrode/squarylium-dye Langmuir-Blodgett (SQ LB) films/bottom aluminum electrode indicated four kinds of conductivity depending on the evaporation conditions of the top gold electrode. The current densities of two, which showed conductance switching, of the four samples were 30–40 µA/cm2 and 20–30 mA/cm2 in the ON state. In the former case, the dependence of conductance switching voltage on the number of SQ LB films and ultraviolet-visible absorption spectra were studied. The results revealed that conductance switching phenomena were induced at the interface between the top gold electrode and SQ LB films, and caused by the presence of H-like aggregates in SQ LB films.

Photolysis of unsubstituted and p‐methoxycarbonyl substituted 2‐methyl‐1‐phenylprop‐2‐en‐1‐one copolymers in solution

SYNOPSIS A new monomer, methyl 4-(2-methyl-l-oxoprop-2-en-l-yl)benzoate (p-(methoxycarbony1)phenyl isopropenyl ketone, MeOCO-PIPK), was synthesized and copolymerized with styrene and methyl methacrylate (MMA). The copolymers of MeOCO-PIPK and 2-methyl1-phenylprop-2-en-1-one (phenyl isopropenyl ketone, PIPK) with styrene and MMA were photoIyzed by deep-, mid- and near-UV light in dilute solution; and the quantum yields of scission, &, and the UV absorption spectra were measured. The p-methoxycarbonyl substitution increased the molar extinction coefficients of the ketone monomer units extensively, but slightly lowered the 4s values in styrene and MMA copolymers. This is expected to increase the net sensitivity of solid films of the polymers. The was found independent of the wavelength, despite the concurrent absorption by styrene units in the styrene copolymers. Larger & values were obtained for the MMA copolymers than the corresponding styrene copolymers. Solvents with larger dielectric constants gave larger & for the copolymer of MMA with PIPK; but when the dielectric constants were similar, lower 4s values were observed in the solvents with more easily abstractable hydrogens. A large bleaching effect was seen in MMA copolymers, which should make possible the formation of resist patterns with steep profiles when used in photolithography. 0 1996 John Wiley & Sons, Inc.

Energy Quenching Effects on Dry-Etching Durability of Alicyclic-Aliphatic Copolymers and Polymer Blends Enhanced by Polymer-Chain Entanglement

A correlation between the macromolecular structure and dry-etching durability is essential to design a resist of high performance. Ohnishi and ring parameters are known to be useful for estimating the durability, but some limitations are apparent, since the etching rate of a multicomponent matrix polymer is not only dependent on the composition. Previously, we have demonstrated that the etching rates of copolymers and polymer blends, which are composed of fragile aliphatic monomer and stable aromatic or alicyclic monomer units, are lower (the durabilities are higher) than the values calculated from those of the constituent homopolymers with the assumed wt% additivity. In this study, we prepared methyl methacrylate [MMA]/tricyclodecanyl methacrylate [TCDMA] copolymers of various compositions, and attempted to evaluate the dependence of etching rates on TCDMA content. The dependence was found to be inconsistent with those in the cases of α-methyl-styrene, 2-vinyl-naphthalene, and isobornyl methacrylate copolymers and polymer blends reported in the previous papers.

A Surface-Silylated Single-Layer Resist Using Chemical Amplification for Deep-Ultraviolet Lithography: I. Limited Permeation of Si Compounds from Vapor Phase*

A single thick layer of poly(vinyl phenol) containing onium salt was surface-silylated uniformly through contact with hexamethyl-cyclotrisilazane or hexamethyl-disilazane in solution to obtain a bilevel structure, similarly to a previous silylation study in the vapor phase. Silicon atoms were effectively incorporated into the surface sublayer by limited permeation of the solute and reaction with –OH to form –O–SiR3. The O2 reactive ion etching (RIE) durability of the silylated sublayer of 170–220 nm thickness was 15–38 times as high as that of the unsilylated bulk layer. The resist layer was patterned by 5–10 mJ/cm2 deep ultraviolet exposure, chemically amplified desilylation during postexposure baking, and wet development with alkali to remove the surface sublayer in the exposed area, forming a shallow, recessed image. When the layer, particularly that silylated with hexamethyl-disilazane, was plasma-developed by O2 RIE, the bulk layer in the exposed area was clearly blanked to the substrate to give a positive-tone image with a high aspect ratio.

Application of Hammett Equation to Decomposition Reaction of Various Photosensitive Diazo Compounds on Iron Surfaces

種々の感光性ジァゾ化合物のポーラログラムを測定した。ポーラログラムの半波電位をpHに対してプロットすると直線が得られ,直線の勾配は種々のジアゾ化合物に対してほぼ同じであった。このグラフから酸化還元電位を得た。ポーラログラムの半波電位をHammett式の置換基定数(б)に対してプロットすると直線が得られた。このことからHammett式が種々の感光性ジアゾ化合物の半波電位に対して適用され,また反応定数(ρ)は0.34となった。種々の感光性ジアゾ化合物は鉄粉表面によって分解される。ジアゾ化合物と鉄粉の反応は1次反応であった。Hammett式は種々の感光性ジアゾ化合物と鉄粉との反応速度に対しても適用され,反応定数(ρ)は0.93となった。この反応の反応速度は,ジアゾ化合物の光分解における量子収率と平行にならなかった。