Hiroshi Mashima

A technique for uniform generation of very-high-frequency plasma suited to large-area thin-film deposition

Two very-high-frequency powers between which the phase difference is varying in split of time are supplied to a ladder-shaped electrode through multiple feeding points located at symmetrical positions of the electrode to generate a large-area uniform plasma. Theoretical calculations of the voltage distribution at several phase difference show good agreement with experiments. Plasma emission uniformity within ±15% is demonstrated at 60MHz for the substrate size of 1.4×1.1m, with nitrogen gas of 10Pa.

Characteristics of VHF excited hydrogen plasmas using a ladder-shaped electrode

Abstract A VHF excited hydrogen plasma was produced with a ladder-shaped electrode whose excitation frequency ranged up to 100 MHz for gas pressures of 40–200 mTorr and the plasma parameters were measured with a Langmuir probe. When the excitation frequency was increased, the electron density increased and the electron temperature decreased. The pressure dependence of the electron temperature at excitation frequencies of 65 and 100 MHz was different from the usual relationship: the electron temperature tended to increase with increasing pressure.

Production of Inductively Coupled RF Plasma Using a Ladder-Shaped Antenna

A radiofrequency (RF) excited H 2 plasma is produced using a ladder-shaped antenna which is positioned within a plasma chamber and the fundamental characteristics of the plasma are examined. The potential and current fed to the antenna are almost in phase. The plasma parameters are measured as a function of RF power, gas pressure and gas flow rate with a Langmuir probe. It is found that the plasma density is uniform within ±10% over 300 mm. Furthermore, increases in the frequency of the RF power source lead to increases in the plasma density. When a mesh grid is installed between the antenna and the substrate, the plasma density and the plasma potential decrease.

Characteristics of Very High Frequency Plasma Produced Using a Ladder-Shaped Electrode

A very high frequency (VHF) excited H2 plasma is produced with a ladder-shaped electrode consisted of 17 rods and the plasma parameters are measured with a movable Langmuir probe. When the discharge frequency (~120 MHz) of the RF power source is increased, the plasma density increases while the electron temperature decreases. The position of the RF connections and the shape of the rod, particularly at higher frequencies are found to affect the distribution of the ion saturation current. The uniformity of the ion saturation current of ±17.2% over a distance of 150 mm is achieved at 120 MHz.

Uniformity of VHF plasma produced with ladder shaped electrode

The uniformity of very high frequency (VHF) plasma produced with the ladder shaped electrode was examined by changing VHF power feeding positions for different discharge frequencies. It was found that the plasma uniformity strongly depends on how to feed the VHF power. Potential distributions on the ladder shaped electrode were calculated using the moment method and compared with measured spatial profiles of the ion saturation current. It was found that when the number of feeding positions are increased, the plasma uniformity is improved.

Characteristics of Very High Frequency Plasma Produced with Ladder-Shaped Electrode at High Pressure

A very high frequency (VHF) plasma was produced with a ladder-shaped electrode at high pressure and plasma parameters such as the density and temperature of electrons were measured as a function of pressure using a Langmuir probe. A VHF power source with a frequency of 60 MHz was used and the power was up to 450 W. When the pressure was increased from 0.3 Torr to 4 Torr, the plasma density decreased at high pressure, while the electron temperature was approximately 10 eV at high pressure. Furthermore, Langmuir probe characteristics indicated that there exist many negative ions at high pressure.

Characteristics of VHF-excited SiH4/H2 plasmas using a ladder-shaped electrode

Abstract A VHF-excited SiH 4 /H 2 plasma was produced using a ladder-shaped electrode. By measuring the plasma parameters with a heated Langmuir probe, the effect of hydrogen dilution on SiH 4 /H 2 VHF plasma characteristics was investigated. The ion density of the SiH 4 /H 2 plasma was higher than that of the H 2 plasma. The electron temperature tended to decrease for high H 2 dilution rate and became minimum at H 2 flow rate/(SiH 4 flow rate+H 2 flow rate)=91%, corresponding to the H 2 dilution rate near the deposition condition of hydrogenated microcrystalline silicon films. Negative ions exist in the SiH 4 /H 2 plasma. The negative ion density increased with increases in the radio frequency power. At the H 2 dilution rate where the negative ions exist, the electron temperature was high approximately 1.5 eV compared with that at other dilution rates.