Shigekazu Tada

Measurement and control of absolute nitrogen atom density in an electron-beam-excited plasma using vacuum ultraviolet absorption spectroscopy

The absolute nitrogen (N) atom density in an electron-beam-excited plasma (EBEP) operating at an ultralow pressure has been investigated by vacuum ultraviolet absorption spectroscopy, employing a microdischarge hollow-cathode lamp. The measured N atom density was estimated to be around 6×1011 cm−3, and the dissociation fraction was 4.9% at a N2 pressure of 0.05 Pa, an electron-beam current of 10 A, and an electron-beam acceleration voltage of 120 V. The EBEP potentially enables us to control the electron density and electron energy independently with the electron-beam current and electron-beam acceleration voltages, respectively. It was found that N atom densities increased with increasing electron-beam current and electron acceleration voltage under low-pressure conditions. The EBEP shows great promise as a N atom source operating at an ultralow pressure.

A large-area ECR processing plasma

This paper describes an improved large-diameter electron cyclotron resonance (ECR) source which employs a strip-bar antenna. By launching a 2.45 GHz microwave near the magnetic field of permanent magnets of alternative polarity set along closed loops, an ECR plasma is produced. The source diameter is 30 cm. The characteristics of an oxygen plasma produced with this modified source are an electron density of , electron temperature of 3 eV and space potential with respect to the chamber wall of less than 20 V. A high plasma density of uniformity within % over 30 cm is achieved.

Investigation of Nitrogen Atoms in Low-Pressure Nitrogen Plasmas Using a Compact Electron-Beam-Excited Plasma Source

We developed a new compact electron-beam-excited plasma (EBEP) source with a multihole grid. The source can be reliably operated under low-pressure conditions by controlling the electron-beam current and electron-beam energy independently. In this study, we applied the compact EBEP source to the generation of nitrogen plasma. The absolute nitrogen (N) atom densities in the plasma were evaluated using vacuum ultraviolet absorption spectroscopy (VUVAS) with a high-pressure microdischarge hollow cathode (MHCL) as a light source. The electron density and electron temperature were measured using a Langmuir probe. The behavior of N atom densities and electron densities in the plasma are discussed.

Deposition of Diamond-Like Carbon Using Compact Electron-Beam-Excited Plasma Source

We have deposited hydrogenated amorphous carbon (a-C:H) films called diamond-like carbon (DLC) on an electrically floating disk using a compact electron-beam-excited plasma (EBEP) employing toluene and ethylene as feed gases. Since the EBEP source enables us to control the ion sheath bias on the floating substrate by changing the electron-beam energy, the substrate ion bombardment energy needed to form the DLC film can be determined without applying an additional bias power supply such as RF. The relationship among the DLC film properties, the deposition rate and the electron-beam acceleration voltage for both feed gases has been investigated. In order to achieve uniform deposition on a disk of 80 mm diameter, the optimization of the compact EBEP source has been examined as well. A high-quality DLC film with good film uniformity on the disk was synthesized at high acceleration voltage employing toluene gas.

Cleaning of glass disk in oxygen plasma by using compact electron-beam-excited plasma source

We have applied a compact electron-bean-excited plasma (EBEP) source to the cleaning process for a glass disk. Since the EBEP enables us to control the ion sheath bias on the floating substrate by changing the electron-beam energy, the substrate ion bombardment energy to perform a reactive ion etching (RIE) can be determined without applying additional bias power supply such as RF. The source system has been modified in several ways so that it can be reliably used in the O2 plasma for a long time. In order to evaluate the cleaning capability of the source system, the etch performance of carbon film was investigated. It was found that the etching rate increased with electron-beam current and electron acceleration voltage. The etch rate of 4 nm/s was obtained at Va of 100 V and Ia of 2.5 A.

A rectangular large ECR plasma source

Abstract Large-area ECR processing plasmas have been developed. Magnetic fields are composed of permanent magnets located along closed lines, inverting the polarity line by line. At first a new type of microwave launching system which consists of a dielectric plate and metal bars was tested, by using a discharge chamber of circular geometry in a diameter of 30 cm. It was verified that the launcher was useful in the production of a large-area plasma in a wide range of gas pressures. By using this type of launcher, a plasma in a rectangular geometry with dimensions of 40 × 50 cm was generated. Basic data which lead to the solution used to obtain a large rectangular uniform plasma (uniformity better than ±5%) were obtained.