Shigemitsu Maruno

Model of leakage characteristics of (Ba, Sr)TiO3 thin films

We have investigated the dependence of leakage current and capacitance of Pt/Ba0.5Sr0.5TiO3/Pt capacitors on annealing temperature under high vacuum conditions. It is observed that leakage currents increase asymmetrically for negative and positive bias voltage with increasing annealing temperature. A model of leakage current and capacitance characteristics has been proposed on the assumption of generation of oxygen vacancies by annealing at the interfaces of the dielectric film adjacent to the Pt electrodes. The model predicts the oxygen vacancies of about 1020 cm−3.

Nanostructure fabrication using the selective thermal desorption of SiO2 induced by electron beams

It has been found that selective thermal desorption of SiO2 on Si (111) substrate is induced by electron‐beam irradiation. By using this selective thermal desorption, a nanofabrication technique has been realized by focused electron beams. Open windows of 10 nm width in a SiO2 film have been fabricated by this technique. A pattern transfer from the open windows to thin Si films has also been performed by Si growth and subsequent heating. This has produced Si wires of 10 nm width.

Observation of oxide/Si(001)-interface during layer-by-layer oxidation by scanning reflection electron microscopy

We have found that terrace contrast of oxidized Si(001) substrate observed with a scanning reflection electron microscopy (SREM) is reversed by progress in thermal oxidation by one atomic layer of Si. The cause for such terrace contrast reversion is that reflection electron intensity depends on Si-bond direction at oxide/Si interface. This fact was confirmed by calculations based on a multiple scattering theory. The motion of oxide/Si-bulk interface can be, thus, observed by SREM. The reversion and continuous change of the terrace contrast indicate that oxidation occurs monolayer by monolayer on Si(001) substrate.

Gas source MBE growth of InP

We report the electrical and optical properties of InP epilayers grown by gas source molecular beam epitaxy (GSMBE) using trimethylindium (TMI) and phosphine (PH3) under various growth conditions. Reflection high-energy electron diffraction (RHEED) intensity oscillations during the growth of InP are also described. It is found that high quality epilayers are obtained at about 490°C, and at this temperature the RHEED intensity oscillations with periods of more than 700 are observed.

Drivability improvement on deep-submicron MOSFETs by elevation of source/drain regions

Deep submicron MOSFETs with elevated source/drain (S/D) structures, where S/D extension regions were partially elevated besides deep S/D regions, were fabricated by use of Si selective epitaxial growth technique. As fairly compared with a well-developed conventional MOSFET, we clarify an advantage of the elevated S/D structures, i.e., improvement upon driving performance with keeping excellent short-channel characteristics, which is enhanced for decrease in gate sidewall spacer width. The experimental results are explained in terms of the reduction in S/D parasitic resistance by addition of the Si epitaxial layer where the impurity profile is suitable.

Selective thermal decomposition of ultrathin silicon oxide layers induced by electron-stimulated oxygen desorption

The mechanism of electron-beam-induced selective thermal decomposition of ultrathin oxide layers on Si surfaces was studied by scanning reflection electron microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. We found that the change in the oxide layer composition caused by electron-stimulated oxygen desorption accounted for the selective thermal decomposition, where nanometer-scale voids were densely generated at a low heating temperature (720 °C). This implies that oxygen desorption from the oxide layers promotes the formation of a volatile oxide (SiO), and generates void nucleation sites.

Threshold height for movement of C60 molecules on Si(111)-7×7 with a scanning tunneling microscope

Scanning tunneling microscope has been employed for intentional movement of C60 molecules adsorbed on Si(111)‐7×7 surface. Threshold conditions at which a C60 molecule starts moving from its adsorption site are investigated in relation to tunnel current and tip bias voltage. We find that there exists threshold height for the movement process. The threshold height estimated from a planar electrode model is in agreement with the vertical height of the adsorbed C60 molecules. Present results evidence that direct contact or close proximity between a mechanical probe and C60 molecules is required for movement of the molecules to occur.

Parasitic Resistance Reduction in Deep Submicron Dual-Gate Transistors with Partially Elevated Source/Drain Extension Regions Fabricated by Complementary Metal-Oxide-Semiconductor Technologies

Deep submicron dual-gate metal-oxide-semiconductor field-effect transistors (MOSFETs) with partially elevated source/drain (S/D) structures were fabricated using complementary MOS (CMOS) technologies. In comparison with well-defined conventional MOSFETs, it is revealed that the drivability is appreciably enhanced by the S/D elevation and, further, that a p-channel MOSFET gains more from the S/D elevation than an n-channel MOSFET. Investigation of the parasitic resistance is consistent with the results of the transistor characteristics.

Electron-Beam-Induced Selective Thermal Decomposition of Ultrathin SiO2 Layers Used in Nanofabrication.

We used ultrathin SiO 2 layers less than 1 nm thick for nanofabrication. In this method, nanometer-scale patterning onto the oxide layers was achieved by electron-beam (EB)-irradiation and subsequent thermal heating (EB-induced selective thermal decomposition). We examined the delineation mechanism by using scanning reflection electron microscopy (SREM), and Auger electron and X-ray photoelectron spectroscopy (AES and XPS). We found that the change in the oxide layer composition caused by electron-stimulated oxygen desorption (ESD) from the oxide layers accounted for the selective thermal decomposition, by which nanometer-scale voids were densely generated.

Effect of hydrogen molecules on growth rates of GaAs in gas source molecular beam epitaxy

We observed intensity oscillations of reflection high-energy electron diffraction during growth of GaAs using triethylgallium (TEG) and arsine (AsH3). The oscillation period increased with increasing AsH3 flow rate. We found that introduction of H2 or N2 during the growth also caused a decrease in the growth rate. The growth rate reduction is explained by assuming that transient residence of H2 or N2 molecules on the growing surface impedes adsorption of TEG molecules.