Microfabricated inductively coupled plasma (mICP) generators, operating at
690 and 818 MHz, have been constructed and characterized. The mICP
consists of a single-turn coil that is 5mm in diameter and a microfabricated
matching network. Ion densities of ~9 × 10(10) cm−3 in argon at 400mTorr
consuming only 1W were obtained. This ion density is three times larger
than previous mICP sources under the same conditions. The influence of the
frequency of operation and the coupling coefficient on the power efficiency
has also been studied. Contrary to what was observed in former generations
of mICP sources operating at lower frequencies, the efficiency of the new
mICP sources decreases as the frequency increases. A model that
incorporates the electron inertia, the power dependence of the plasma
resistance and the frequency dependence of the coil resistance agrees with
the new experimental results as well as with the results of previous mICP
sources. It was also observed that bringing the coil closer to the plasma
increases the coupling coefficient of the ICP sources and thereby improves
the efficiency of the device. The improvement in efficiency, however, is
limited by the non-scalable plasma sheath width near the coil.
History
School
Mechanical, Electrical and Manufacturing Engineering
Citation
IZA, F. and HOPWOOD, J.A., 2002. Influence of operating frequency and coupling coefficient on the efficiency of microfabricated inductively coupled plasma sources. Plasma Sources Science and Technology, 11, pp. 229–235.