Hiromu Takatsuka

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.