Koichi Ikeda

Stress evaluation of radio-frequency-biased plasma-enhanced chemical vapor deposited silicon nitride films

Stress is evaluated for silicon nitride films prepared by rf-biased plasma-enhanced chemical vapor deposition. The total stress of the films shows a change from tensile to compressive with increasing applied rf bias during film deposition. The biaxial elastic moduli and linear thermal expansion coefficients of the silicon nitride films are determined by measuring the temperature dependence of the total stress of films deposited on two different substrate materials. Both the biaxial modulus and linear thermal expansion coefficient are dominantly related to film density. The intrinsic stress of the silicon nitride films calculated using these values is very close to the total stress. The intrinsic tensile stress originates from spontaneous densification during film growth, while the compressive stress results from incorporated atoms that are accelerated and implanted into the films by rf-bias induced plasma potential.

The Effects of Alkoxy Functional Groups on Atmospheric‐Pressure Chemical Vapor Deposition Using Alkoxysilane and Ozone

The effects of alkoxy functional groups on atmospheric-pressure chemical vapor deposition (APCVD) using alkoxysilane and ozone are investigated from the standpoint of the molecular structure of the alkoxysilane molecules. Deposition rate and step coverage are evaluated for three kinds of alkoxysilane sources [(RO) 4 Si]: (CH 3 O) 4 Si, (C 2 H 5 O) 4 Si (called TEOS), and ((CH 3 ) 2 CHO) 4 Si. The addition of three kinds of alcohols, CH 3 OH, C 2 H 5 OH, and (CH 3 ) 2 CHOH, to the TEOS/O 3 system is also investigated. Both the deposition rates and step coverage are associated with the RO- functional groups of the alkoxysilane molecule. (CH 3 O) 4 Si, which contains the smallest alkoxy (RO-) groups, has the highest deposition rate and the best flow characteristics among the three silicon sources. With added alcohol: (i) the OH- group scavenges ozone molecules and affects the deposition rate, and (ii) the RO- group affects only the step coverage. The flow property is also affected by adding RO- fragments in reaction system

High Power Travelling-Wave Type Ultrasonic Motor

We have performed an experiment aimed at developing a high power ultrasonic motor based on a thin, lightweight, travelling-wave type design. This paper presents a detailed analysis of experimental results. Three prototype motors of the improved type were fabricated, having outer diameters of 50, 70 and 90 mm. Compared to a motor employing a piezoelectric element of the same outer diameter and the same resistive resin material as conventional types of motors, approximately twice as high maximum torque and four times as high maximum output power have been obtained with the prototype motors. It has also been confirmed that these motors have sufficient durability to withstand high-loads.

A field study of the human support robot in the home environment

As concern for Japans aging population and shrinking workforce continues to mount, many researchers are focusing on nursing and healthcare-related robots to help ease the burden on society. In order to successfully integrate robots into the home environment to coexist with family members, three features are considered essential: safe interaction, a compact and lightweight body, and a simple interface. In this paper the authors introduce a robot that possesses these qualities: the human support robot (HSR). The current prototype HSR is designed to support independent living of persons with limited limb mobility. This paper discusses the development of the HSR and the results of user testing conducted in the homes of two persons with disabilities.

Characteristics of Silicon Dioxide Films on Patterned Substrates Prepared by Atmospheric‐Pressure Chemical Vapor Deposition Using Tetraethoxysilane and Ozone

Atmospheric-pressure chemical vapor deposition of silicon dioxide films, using tetraethoxysilane and ozone sources, can produce a flowing-like step coverage on a patterned substrate. We evaluate the characteristics of silicon dioxide films deposited on a patterned substrate and compare them with those on a flat surface. Thermal desorption spectroscopy detects synchronous m/e = 48 and m/e = 64 fragments only in silicon dioxide films deposited on patterned substrate. The spectral change for the mle = 32 fragment is also detected. The contaminants, which desorb the parent species of m/e = 48 and m/e = 64 fragments during thermal desorption spectrometry, are localized in the bottom corner of the steps on patterned substrates. In Fourier transform infrared spectra of the film on patterned substrates, the peak attributed to the Si-O stretching vibration mode shifts and spreads to lower wave numbers.

Effect of Added Ethanol in Atmospheric-Pressure Chemical Vapor Deposition Reaction Using Tetraethoxysilane and Ozone

Ethanol added in tetraethoxysilane (TEOS)-ozone ( O3) atmospheric-pressure chemical vapor deposition (APCVD) reaction is found to affect both deposition rate and step coverage characteristics. The added ethanol decreases the effective ozone concentration in the gas phase; that is, it acts as an ozone scavenger. In the region of flow-shaped step coverage, both the deposition rate and step coverage were enhanced simultaneously. These results suggest that the added ethanol also contributes to the formation of reaction intermediates which affect the flow-shaped step coverage. In addition, it is considered that reaction between these intermediates and ozone molecules is necessary for flow-shaped step coverage.

TiN thin film prepared by chemical vapor deposition method using Cp2Ti(N3)2

Two kinds of chemical vapor deposition (CVD) processes are described for depositing a titanium nitride (TiN) thin film using a biscyclopentadienyltitanium diazide (Cp2Ti(N3)2) source. One is photo-assisted CVD and the other is thermal CVD. The CVD-TiN films are evaluated using thermal desorption spectroscopy and Auger electron spectroscopy. The results reveal that the films include hydrocarbon components consisting of five carbon atoms, and nitrogen atoms desorbed at temperatures over 600°C, and then Ti-C bonds are formed in the films. The film composition (N/Ti) is affected by nitrogen partial pressure. This relationship is significant at substrate temperatures above 400°C. Light irradiation makes it possible to deposit the film at below 350°C. These results indicate that the photo-assisted CVD is effective in making high-quality TiN thin film at low temperature region.

Characteristics of Silicon Dioxide Film Prepared by Atmospheric-Pressure Chemical Vapor Deposition Using Tetraethoxysilane and Ozone with Alcohol Addition

We evaluate the characteristics of silicon dioxide film deposited by atmospheric-pressure chemical vapor deposition (APCVD) using tetraethoxysilane and ozone ( TEOS/O3) with alcohol addition and the role of the alcohol in the reaction system using ethanol- D6. The deuterium substituted ethanol, like normal ethanol, decreases the effective ozone concentration. Secondary ion mass spectroscopy (SIMS) analysis detects a uniform distribution of hydrogen and deuterium incorporated into the deposited film. Fourier transform infrared spectroscopy (FT-IR) spectra show the relationship between the content of the terminal groups in the film and the effective ozone concentration. Three states in thermal desorption spectroscopy (TDS) spectra are characterized: water absorbed after film deposition, water absorbed during film deposition, and terminal groups (i.e., Si-H and Si-OH) in the film in order of annealing temperature. Moreover, it is found that the third state contains two peaks due to deuterium substitution. One of the peaks in the third state is associated with the flowing-like profile formation.

Human support robot (HSR)

There has been an increasing interest in mobile manipulators that is capable of performing physical work in living spaces worldwide, corresponding to population aging with declining birth rates with the expectation of improving quality of life (QOL). Research and development is a must in intelligent sensing and software which enable advanced recognition, judgment, and motion to realize household work by robots. In order to accelerate this research, we have developed a compact and safe research platform, Human Support Robot (HSR), which can be operated in an actual home environment. We assume that overall R&D will accelerate by using a common robot platform among many researchers since that enables them to share their research results. In this paper, we introduce HSR design and its utilization.

Behavior of Alkoxy-Functional Groups on Atmospheric-Pressure Chemical Vapor Deposition Using Alkoxysilane and Ozone

Behavior of alkoxy-functional [RO-] groups in an atmospheric-pressure chemical vapor deposition (APCVD) reaction using alkoxysilane and ozone is evaluated by alcohol addition. The RO- groups from the alcohol affect the flow characteristics of the APCVD reaction. Formation of a flowing-like profile can be accelerated by increasing the partial pressure of RO- groups in the reaction system when the added RO- groups are of the same size as, or smaller than, the RO- groups of silicon sources. When acceleration occurs, the amount of carbon and hydrogen atoms from RO- groups of added alcohols incorporated in the deposited film increases. Thermal desorption spectroscopy (TDS) shows three states for the carbon incorporated in the deposited film. Water desorption, which is related to the incorporated hydrogen, is also measured. Hydrolysis occurs at the residual terminal groups (i.e., Si-H and Si-OH), which are associated with the flow characteristics.