Langmuir probe diagnostics of a microfabricated inductively coupled plasma on a chip

The experimental values for electron temperature and plasma density are measured in a microfabricated, inductively coupled plasma on a chip (ICP). The miniature ICP system consists of a planar plasma source that is microfabricated on a glass wafer and a miniature aluminum vacuum chamber (φ=6 mm). A reliable Langmuir probe diagnostic for microplasma reactors was developed because classic probe measurements would be hindered by the small plasma volume, the small surface area of grounded reactor walls, collisional ion sheathes, and the radio-frequency (rf) interference from the high-frequency power supply. Once the ion density and electron temperature are determined, the neutral gas temperature was estimated to be nearly equal to room temperature. At low pressures, one finds that the plasma sheath width limits the dimensional scaling of the reactor, since the sheath is, typically, ∼0.6 mm. The plasma operates from 0.1 to 10 Torr, and requires less than 3 W of transmitted power at a frequency of 493 MHz. Dire...