Yoichi Domoto

High quality diamond like carbon thin film fabricated by ECR plasma CVD

Diamond like carbon (DLC) films have been fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR CVD). Low temperature (less than 70°C) fabrication of the DLC films, with a hardness of more than 3000 Hv and a high deposition rate of more than 80 nm/min, was achieved by applying a bias voltage during deposition to accelerate the ion impinging energy to the substrate. Furthermore, an attempt was made to fabricate ultrathin DLC films for protective coating purposes. Ultrathin DLC films by this method with a thickness of 10 nm exhibited excellent wear characteristics and chemical inertness, indicating their usability as protective coating for electronic devices.

Advanced fabrication technologies of integrated-type structure for a-Si solar cells

Abstract This paper proposes a new advanced fabrication technology for a low-cost integrated-type a-Si solar cell. Integrated-type cells provide many advantages and have been industrialized with a laser patterning method. However, a higher throughput and more efficient patterning method was required for applying a-Si solar cells to a power generating system. Plasma CVM (Chemical Vaporization Machining) was first applied to advanced patterning because of its advantages of high speed and selectivity. In this method, a plasma generated under high pressure localizes near the wire electrode and concentrates reactive radicals. As a result, we achieved an etching rate of more than 1 μm/s and selective patterning of a 200 μm-wide a-Si layer in 1 s multiline patterning was also developed for large-area modules.

High-Rate Deposition of Amorphous Silicon Thin Films by Atmospheric Pressure Plasma Chemical Vapor Deposition. (1st Report). Design and Production of the Atmospheric Pressure Plasma CVD Apparatus with Rotary Electrode.

A new technique for high speed a-Si deposition using the atmospheric pressure plasma with the cylindrical rotary electrode was developed. The advantages of using rotary electrode are as follows; 1) the reactant gases can be introduced efficiently into the small gap between the electrode and the substrate and 2) a large rf power can be supplied without thermal damage of the electrode. A 150 MHz VHF power supply was employed to avoid the ion bombardment of the electrode and the substrate. In the consequence of these advantages, high density radicals are produced and high quality amorphous silicon films can be deposited with high growth rate. The silicon films were fabricated in gas mixtures containing helium, hydrogen and monosilane. They were investigated by Raman spectroscopy and scanning electron microscopy (SEM). The results showed that amorphous silicon films with uniform structure were grown on the glass substrates. The maximum deposition rate was 38nm/s, which was extremely faster than those of the previous techniques. It was also found from the SEM obsevation that the thickness of the silicon films were uniform and no particles were observed inside the films.

High Speed Deposition of Amorphous Silicon Film by Atmospheric Pressure Plasma Chemical Vapor Deposition (3rd Report). Electrical and Optical Properties of a-Si Films Fabricated at Very High Deposition Rate.

Electrical and optical properties of amorphous silicon (a-Si) films fabricated at very high deposition rate using an atmospheric pressure plasma CVD method with rotary electrode were evaluated for applying to the electric devices. As the results, it was found that a-Si films with this method have good properties such as high photo sensitivity (σph/σd-106 at deposition rate of 0.3μm/s). And the optical gap (Eopt; determined (αhv)1/3 versus hv plot) was about 1.5 - 1.6 eV which were similar to those of a-Si films fabricated by the conventional plasma CVD method at low pressure. With increasing the deposition rate, the Eopt decreased and the hydrogen content in the a-Si films increased, and this tendency was contrary to that of the general a-Si films. These results indicate that the structure of a-Si films with this method include much disorder configuration which narrowed the Eopt. However, enough hydrogen in the films terminated the dangling bonds and caused the reduction of defect density. In conclusion, it was thought that the atmospheric pressure plasma CVD method could fabricate the device grade a-Si film at very high deposition rate.

Surface Modification of Electric Shaver Foil using Ion Beam.

The technique of surface modification using an ion beam is applied to the tool by using the IAD method, the IVD method, and ion plating. In these methods, however, substrate temperature rises due to ion irradiation during the process. A new fabrication method for preparing ceramic thin films named Interface Controlled Vapor Deposition (ICVD) has been developed and makes low temperature fabrication possible. In practical application, electroforming Ni is a good material for a shaver foil. However, the hardness of the electroforming Ni foil increases at high temperatures and this can shorten the life of the shaver foil. So, the ICVD method was applied to the development of a high quality zirconium nitride ceramics coated shaver foil, which has excellent mechanical properties such as surface hardness, wear resistance, friction coefficient and corrosion resistance.

Reaction Analysis of Nitrogen Molecules and Metals in the Fabrication of the Nitride Ceramic Thin Film using ab initio Molecular Orbital Method.

In a nitride ceramic thin film, the fabrication of AIN and ZrN thin films was attempted by an Ar ion beam sputtering method. The ZrN thin film was fabricated by sputtering a Zr target in a nitrogen atmosphere, while the Al and nitrogen reaction required the bombardment of nitrogen ions. Fabrication for both was based on the reaction between nitrogen and Al or Zr atoms. Accordingly, clarifying the difference in reactions between nitrogen and Al or Zr required a theoretical analysis by an ab initio molecular orbital method. An ab initio molecular orbital method was used to analyze the reaction of nitrogen molecules to Al atoms or to Zr atoms. According to the method, the bond order of nitrogen atoms may decrease when they are approached by Zr atoms, while the bond order may change little when the nitrogen atoms are approached by Al atoms. The results of calculations indicated that nitrogen molecules react to Zr atoms more actively than to Al atoms.

Low Temperature Fabrication of ZrN Thin Film using Ion Beam.

Zirconium nitride (ZrN) is one of the nitride ceramics which has many excellent properties, such as hardness, high melting point and chemical stability. Zirconium is reactive material, so it is possible to fabricate the ZrN thin film without irradiating the active particle such as nitrogen ion. So the fabrication of the ZrN thin films was attempted by ion beam sputter (IBS) in which Zr was sputtered by Ar ion beam in a nitrogen atmosphere. It was found that the ZrN thin films could be fabricated at room temperature and the crystallinity of these films could be controlled by varying the pressure of nitrogen. Furthermore, to improve the deposition rate and adherence, the fabrication of the ZrN thin films was attempted by ion beam assisted deposition (IAD) method in which the thin films were formed by evaporating Zr under simultaneous nitrogen ion irradiation. Using this method, the ZrN thin films with good adherence were fabricated at the high deposition rate, and the films were also confirmed to be hard ceramic film with a value of 1 600 HV. Also, it was found that the crystallinity of these films could be controlled by the N/Zr arrival ratio.

Low Temperature Fabrication of AlN Film by Irradiation of Low Energy Ion Beam.

Aluminum nitride (AIN) is expected of useful electronic material because of properties of high temperature stability, chemical stability, high thermal conductivity, high sound velocity and so on. For purposes of fabrication and control of film crystallinity and orientation at low temperature, AIN film was prepared by dual ion beam deposition method. It was found that the bombardment of nitrogen ions was very important for reaction between aluminum and nitrogen, inc.1 that a good oriented AIN film could be formed at room temperature by the precision control of the bombardment of low nitrogen ion energy (100 eV). For stoichiometric AIN, the c-axis orientation depends on the nitrogen ion beam current density and becomes better with the increase of nitrogen ion beam current density. The c-axis orientation of AIN film by this method was independent of the kind of substrates and temperature.

Low temperature fabrication of ceramic film by ICVD method using ion beam

Abstract Interface controlled vapor deposition (ICVD) is a new fabrication method for ceramic thin films that has been developed to achieve both low temperature fabrication and control of the film crystallinity and orientation. The ICVD method makes these possible by strict control of the interface conditions between the substrate and the thin film using an ion beam. This method was applied to the fabrication of zirconium nitride (ZrN) film. The ICVD method consists of two different steps. In the first step, a modification layer is formed by evaporating zirconium under simultaneous nitrogen ion irradiation. In the second step, evaporation alone is continued in a nitrogen atmosphere in order to deposit a second layer. Using this method, ZrN film with good adherence was fabricated at room temperature, and its crystallinity and orientation were controllable. This film was also confirmed to be a hard ceramic film with a value of 1600 Hv. Furthermore, a high quality ceramic coated shaver foil with excellent properties was developed by the ICVD method.