O2 Plasma Irradiation Research Articles

Effects of Electron-Cyclotron-Resonance Oxygen Plasma Irradiation on Properties of Insulator/Ge-Semiconductor Interfaces Prior to Germanium Nitride Formation

Electron-cyclotron-resonance (ECR) oxygen (O2) plasma was irradiated onto the surface of germanium (Ge) substrates prior to germanium nitride (GeNx) formation. Germanium metal–insulator–semiconductor (Ge-MIS) structures with a 5-nm-thick silicon nitride/2-nm-thick GeNx gate insulator stack fabricated by ECR plasma nitridation and sputtering deposition without substrate heating were electrically and physically characterized. Although ECR O2 plasma irradiation onto the surface of Ge substrates caused no significant difference in the chemical state of GeNx/Ge interfaces in X-ray photoemission spectroscopic measurement, irradiation for an appropriate period improved the state of GeNx/Ge interfaces and the electrical properties of Ge-MIS.

Room-Temperature Carbon Nanotube Single-Electron Transistors Fabricated Using Defect-Induced Plasma Process

We propose and demonstrate the “defect-induced plasma process” for the fabrication of the room-temperature-operated carbon nanotube single-electron transistors (CNT-SETs) with the SiO2 protection films on the CNT channels. After introducing of defects in the CNT channels by O2 plasma irradiation through the SiO2 protection films, multi-quantum dots were fabricated in the CNT channels. The electrical properties of the CNT-SETs suggested that the oscillation in the drain currents as a function of the gate voltage was observed at room temperature, as a result of the Coulomb blockade effect. Moreover, we report that the yield of the CNT-SETs depended on the thickness of the SiO2 protection films on the CNT channels for the purpose of obtaining a high yield of CNT-SETs. The results indicate that the high yield of the CNT-SETs is as high as approximately 35% when the SiO2 protection film thickness is 60 nm. Consequently, the defect-induced plasma process is useful for obtaining the high yield efficiency of CNT-SETs operating at room temperature.

シリコンのＤＲＩＥにおける大小開口混在パターン一括加工技術の開発

We have developed a new Si DRIE process, which allows simultaneous etching of both narrow and wide mask opening patterns. MEMS devices often contain a wide range of mask opening sizes ranging from micrometer to millimeter scale on the same chip. Conventional DRIE process suffered from a trade-off between minimizing mask-undercut for narrow grooves and eliminating black Si on an etched bottom surface for large mask apertures. This was caused by nonuniformity in the deposition of the protective polymeric layer during etching in mask aperture areas having different sizes. Our new DRIE process technique, alternating conventional DRIE with O2 plasma irradiation, adds a SiO2 layer onto the polymeric layer. We have ascertained that the new DRIE process can form a SiO2 protective layer of uniform thickness regardless of the mask aperture size. This uniformity is considered a result of equilibrium between surface oxidation and sputtering of oxygen by plasma irradiation. We have demonstrated that our newly developed process allows simultaneous etching of narrow, deep grooves 1 μm wide and 73 μm deep, and wide aperture areas 500 μm square without black Si on the same chip. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(4): 36–43, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10303

Oxygen Permeability of Surface-modified Poly(dimethylsiloxane) Characterized by Scanning Electrochemical Microscopy

Abstract Scanning electrochemical microscopy (SECM) was employed to quantitatively characterize the oxygen permeation behaviors of poly(dimethylsiloxane) (PDMS) and surface-modified PDMS. The mass-transfer process of oxygen from the PDMS substrate to the tip electrode is diffusion limited, whereas the oxygen permeability of PDMS subjected to oxygen plasma treatment or albumin adsorption is critically restricted. Our results suggest that the oxygen permeability of PDMS is possibly affected by O2 plasma irradiation and albumin adsorption at the PDMS surfaces.

Low temperature crystallization of sol-gel derived TiO2 precursor thin films by O2 plasma irradiation

Low temperature crystallization of sol-gel derived TiO2 precursor thin films by O2 plasma irradiation

New DRIE Process with Sidewall Protection Layer Formed by O<sub>2</sub> Plasma Irradiation

The DRIE (Deep Reactive Ion Etching) process is one of the most important processes for MEMS field. Especially, a high aspect ratio etching is essential for state-of-the-art devices. This paper describes a new DRIE process that drastically improves the highest aspect ratio of conventional DRIE process. The conventional process deposits a protection layer not only on a trench sidewall, but also on a trench bottom. This isotropic deposition causes a limitation of aspect ratio. To avoid this situation, we have developed a new process that alternately repeats the conventional DRIE process and a O2 plasma irradiation which forms a thin SiO2 layer inside the trench within a same chamber. The SiO2 layer remains on the sidewall during the DRIE proceeds while it on the bottom is removed at the beginning of each DRIE. Therefore, the etching anisotropy is improved. A switching between the conventional DRIE and the O2 plasma irradiation needs only to change introducing gasses. This simple process can widen a possibility of the conventional DRIE.

酸素／ヘリウムグロー放電によるシリコンの表面酸化とバブル生成

To produce silicon oxide layer with bubbles, O2 and He DC glow discharges were conducted for a p-type (100) silicon wafer. After the plasma irradiation, the depth profile of oxygen concentration and surface morphology of the samples were examined by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM), respectively. In the case of O2 plasma irradiation, the thickness of oxide layer increased with increases of negative bias voltage and substrate temperature. In the case of He plasma irradiation, the bubbles with various diameters were formed on the Si surface. The average size of bubbles increased as the increase of He ion fluence. The size ranged from 0.12 to 0.35 μm. On the other hand, surface density of bubbles decreased when the ion fluence increased. After the He plasma irradiation at RT, the O2 plasma irradiation was conducted at the temperatures of RT and 873 K. The thickness of oxide layer increased compared to the case of only the He plasma irradiation, when the temperature was RT. In the case of 873 K, the bubble was destroyed and an increase of the oxidation thickness was not large as estimated.

Surface Treatment of Indium-Tin-Oxide Substrates and Its Effects on Initial Nucleation Processes of Diamine Films

The effects of several surface treatment techniques for indium-tin-oxide (ITO) substrates on the surface properties and the initial nucleation processes of trisphenyldiamine (TPD) have been investigated. Mechanical rubbing, HCl treatment, and O2-plasma irradiation smoothen the ITO surface and enhance the cohesion of TPD molecules. As-received ITO surfaces promote amorphous structure of the TPD molecules; this results in effective carrier transport, but the substrate surface is too rough on a molecular scale for the fabrication of very thin ( e.g., ≤200 Å) layered structures. Layer-by-layer amorphous nucleation on flat surfaces is a key technology for the fabrication of future organic electroluminescence (EL) device structures with very thin constituent layers. O2-plasma treatment reduces the potential barrier for hole injection from ITO to TPD with moderate cohesion of TPD molecules, and results in brighter EL devices than those on as-received ITO substrates.