Tetsu Okamoto

Characteristics of a Large-Diameter Surface-Wave Mode Microwave-Induced Plasma

A large-diameter unmagnetized argon plasma is generated by an Okamoto cavity operated in a surface-wave mode. A quartz discharge tube (16 cm inner diameter, 12 cm long) is placed inside the cavity. An argon plasma is produced in the discharge tube and effuses in a process chamber. The electron density, electron temperature, ion current density and floating potential in the chamber are measured as a function of spatial position using a Langmuir probe. An electron density over 1011 cm-3, with an electron temperature in the range of 2–3 eV and a floating potential with respect to the chamber wall of less than 5 V is obtained at pressure in the mTorr range with 2.45 GHz, 700 W input microwave power. A high ion current density (over 10 mA/cm2) of uniformity (standard deviation/average) within 4.4% over 16 cm is achieved.

Time-Resolved Electron Energy Distribution Function in Pulsed Surface Wave Plasma Generated by Ring-Slot Antenna

Time-resolved probe measurements of the electron energy distribution function (EEDF) in a substrate (wafer) holder were performed in a pulse-modulated argon plasma of high density (>1011/cm3), low electron temperature (<2 eV) and excellent uniformity (±3% over 24 cm diameter). The plasma was produced by a time-modulated surface wave power with a ring-slot antenna. Microwave power (2.45 GHz, 1 kW max.) was modulated with a square wave pulse of 100 µs duration and 20–90% duty ratio. The temporal evolution of the EEDF was divided into two zones, namely, the zone where the microwave power is turned on (active plasma region: on-time) and that where the power is turned off (afterglow plasma region: off-time). In the first zone, the EEDF shows a fast evolution in which the number of high-energy electrons (high-energy tail of EEDF) increases with time. The second zone is characterized by a significant decrease in the number of high-energy electrons and an increasing EEDF that shifts to low energy values. These characteristics were compared with those of the continuously driven (CW) plasma.

Production of a large-area argon microwave plasma by a ring slot antenna

Abstract A large-area, uniform, low-temperature and high-density microwave argon plasma is produced using a simple flat ring slot antenna without a magnetic field. The plasma production is based on the absorption of the energy of microwave propagating in the dielectric plate (quartz glass) along the plasma surface. The power is coupled to the dielectric plate by azimuthal symmetrical mode. An electron density of >1011/cm3 with an electron temperature