Akihiko Kono

Substrate Temperature Dependence of the Photoresist Removal Rate Using Atomic Hydrogen Generated by a Hot-Wire Tungsten Catalyst

Instead of photoresist removal methods using chemicals, we investigated an environmentally friendly removal method using atomic hydrogen generated by decomposing hydrogen molecules by contact with a hot-wire tungsten catalyst. We set the distance between the catalyst and the photoresist substrate (DCS) at 20, 60, 100 and 120 mm and evaluated the apparent activation energy (EAP) for the reaction between photoresist and atomic hydrogen at each DCS. The EAP was determined from Arrhenius plots of the photoresist removal rate against the average substrate temperature. When DCS was 20 and 60 mm, EAP decreased with increasing catalyst temperature (WT=2040–2420 °C) and was not constant. However, when DCS was 100 and 120 mm, EAP was nearly constant at 19 ±1 kJ/mol without depending on WT. We might obtain the activation energy of about 19 kJ/mol in the reaction of photoresist with atomic hydrogen.

Effective creation of oxygen vacancies as an electron carrier source in tin-doped indium oxide films by plasma sputtering

We have investigated the effect of hydrogen on the resistivity, Hall mobility, and carrier density of ITO films on glass substrates using a low-pressure plasma sputtering method. It was found that a certain hydrogen content in the Ar plasma leads to improvement in the resistivity relating to an increase in the electron carrier density. The improvement is explained by oxide reduction due to the reaction of hydrogen radicals with indium oxide (In2O3). The effect of postannealing on the electrical properties confirmed that the improvement of the resistivity is a result of an increase in oxygen vacancies as the electron carrier source in the ITO film. Oxygen extraction in the initial stages of ITO film growth, due to the glass substrate surface, is suggested to create oxygen vacancies as the electron carrier source for improvement in the resistivity of the films.

Removal of Ion-Implanted Photoresists Using Atomic Hydrogen

In this paper, we investigated the removal characteristic of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of 5 × 10 12 -5 × 10 15 atoms/cm 2 at an acceleration energy of 70 keV using atomic hydrogen, and the hardening mechanisms for the photoresists. All of the ion-implanted photoresists with doses up to 5 × 10 15 atoms/cm 2 were removed without regard for ion species. The removal rates of the photoresists decreased with increasing ion-implantation dose due to hardening of the photoresist surfaces with implantation. The thickness of the surface-hardened layer of the photoresists decreased in the order of B → P → As, and the removal rate increased with decreasing thickness. The energy supplied from the ions to the photoresist concentrated on the surface side in the order of B → P → As, and the impact of the heavier ion on the photoresist was greater than that of the lighter ion. We deduced that the photoresists exhibited carbonization and cross-linkage attributable to the decrease in OH, CH, and 0 1s and the increase in C=C, C 1s, and π-conjugated systems.

Synergistic Formation of Radicals by Irradiation with Both Vacuum Ultraviolet and Atomic Hydrogen: A Real-Time In Situ Electron Spin Resonance Study.

We report on the surface modification of poly(tetrafluoroethylene) (PTFE) as an example of soft materials and biomaterials that occur under plasma discharge by kinetics analysis of radical formation using in situ real-time electron spin resonance (ESR) measurements. During irradiation with hydrogen plasma, simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the C-DB density were observed in real time, where the rate of density change was accelerated during initial irradiation and then became constant over time. It is noteworthy that C-DBs were formed synergistically by irradiation with both vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR technique is useful to elucidate synergistic roles during plasma surface modification.

Order of Reaction between Photoresist and Atomic Hydrogen Generated by a Tungsten Hot-Wire Catalyst

This paper clarifies the reaction order of photoresist removal using atomic hydrogen by investigating the relationship between atomic hydrogen density (nH) and photoresist removal rate (vrmv). Atomic hydrogen was generated by decomposing hydrogen molecules with a tungsten hot-wire catalyst. In the reaction between atomic hydrogen and photoresist, we found that vrmv increases in direct proportion to nH and revealed that the reaction exhibited a first-order kinetics with respect to nH.

Spherical carbon particle growth in a methane plasma

There is strong evidence that the spherical carbon particles composed of graphite carbon onions of ca. 10nm are grown to micron size under the conditions of a heated Si (100) substrate surface exposed to irradiation by a CH4∕Ar plasma. Furthermore, it is described that these carbon particles of micron size are spherically grown in the plasma and then fall to the substrate surface.

Growth mechanism for spherical carbon particles in a dc methane plasma

The growth mechanism for spherical carbon particles of micron sizes observed in a vertically excited CH4∕Ar columnar plasma [F. Shoji, Z. Feng, A. Kono, and T. Nagai, Appl. Phys. Lett. 89, 171504 (2006)] is investigated theoretically, based on a model in which the particles are negatively charged in the plasma sheath region where they grow by capturing graphite onions with a diameter of ca. 10nm and a positive charge. A balance of gravity and electric force keeps the particles in the sheath region during their growth. It is found that the particle radius initially increases linearly with time and then approaches a saturation radius, and that the center of gravity of the particle executes a simple harmonic oscillation about its balance position with a characteristic frequency of the order of 10Hz determined by its specific charge, gravity, and sheath structure.

Spherical carbon liquids generated in a low pressure CH4∕Ar plasma

The authors present a study on spherical carbon particles of micron sizes grown in the plasma sheath as spherical liquids that can be agglomerated by capillary force based on the Laplace pressure. In addition, it is suggested that those spherical carbon liquids with negative charges that are levitating in the sheath region begin to display a collective behavior of Coulomb crystals.

Relationship between interfacial hydrophobicity and hydroxylation activity of fungal cells located on an organic-aqueous interface.

In a liquid-liquid interface bioreactor, fungal cells locate in a hydrophilic polyacrylonitrile microsphere layer on an aqueous-organic interface. In this article, effects of hydrophobicity of the interface on n-decane hydroxylation activity of Monilliera sp. NAP 00702 was examined. (-)-4-Decanol production was significantly enhanced to 132% by addition of polytetrafluoroethylene.

Enhancement of 6-pentyl-α-pyrone fermentation activity in an extractive liquid-surface immobilization (Ext-LSI) system by mixing anion-exchange resin microparticles

The addition of anion-exchange resin microparticles into a polyacrylonitrile (PAN) ballooned microsphere layer drastically enhanced the fermentative activity of Trichoderma atroviride AG2755-5NM398 in an extractive liquid-surface immobilization (Ext-LSI) system. The production of 6-pentyl-α-pyrone (6PP), a fungicidal secondary metabolite, was 1.92-fold higher than the control (PAN alone).