Index of content:
Volume 86, Issue 10, 15 November 1999
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
86(1999); http://dx.doi.org/10.1063/1.371532View Description Hide Description
Plasma uniformity has been recognized as a significant parameter in large-sized high density plasma processing tools, but neutral uniformity issues have received less attention. In this article we show experimental and modeling results which indicate that significant neutral uniformity variations can occur in high density plasma processing tools. The experiments are carried out in both inductively coupled plasma and helicon plasma sources. A movable static pressure gauge is used to obtain the static radial neutral pressure distribution both with and without a discharge present. Without a wafer present in the reactor, significant (∼20%–40%) reductions in neutral pressure are observed in these sources during steady-state plasma operations. This spatially averaged neutral depletion is accompanied by hollow neutral pressure profiles. The degree of on-axis neutral depletion depends upon both plasma density and neutral fill pressure. We show that the “plasma pumping” effect, wherein electron impact ionization of neutral particles is followed by their rapid removal from the plasma by the pre-sheath electric field, can reproduce the experimental results. This effect has the potential to result in large (∼50%) neutral density variation across 300 mm wafers in high density plasma sources.
86(1999); http://dx.doi.org/10.1063/1.371533View Description Hide Description
We report the efficacy and spectrum of an inductively-coupled, radio-frequency discharge in mixtures of magnesium(Mg), hydrogen and argon vapor. The predominantly green emission is dominated by the band of MgH, plus some Mg lines. The discharge operates in a frit-sealed, ∼600 °C alumina cell with a sapphire window, at pressures of 200–600 Pa. The plasma impedance is established from the impedance of the matching network parameters, and the electron temperature is determined from line intensity ratios. Assuming isotropic emission, a maximum energy efficiency (η) of ∼ 10% (efficacy ∼ 90 lm per watt) is achieved, where η is the ratio of visible emission to power delivered to the matching network.