Volume 89, Issue 1, 01 January 2001
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
89(2001); http://dx.doi.org/10.1063/1.1323754View Description Hide Description
Gas breakdown is studied in an atmospheric pressure rf capacitive plasma source developed for materials applications. At a rf frequency of 13.56 MHz, breakdown voltage is largely a function of the product of the pressure and the discharge gap spacing, approximating the Paschen curve. However, breakdown voltage varies substantially with rf frequency due to a change in the electron loss mechanism. A large increase in breakdown voltage is observed when argon, oxygen, or nitrogen is added to helium despite their lower ionization potential. Discussion is given for optimal breakdown conditions at atmospheric pressure.
89(2001); http://dx.doi.org/10.1063/1.1323753View Description Hide Description
Discharge phenomena of a nonthermal atmospheric pressure plasmasource have been studied. An atmospheric pressure plasma jet (APPJ) operates using rf power and produces a stable homogeneous discharge at atmospheric pressure. After breakdown, the APPJ operation is divided into two regimes, a “normal” operating mode when the discharge is stable and homogeneous, and a “failure” mode when the discharge converts into a filamentary arc. Current and voltage characteristics and spatially resolved emission intensity profiles have been measured during the normal operating mode. These measurements show that the APPJ produces an alpha (α) mode rf capacitive discharge. Based upon a dimensional analysis using the observed characteristics, a rough estimate is made for plasma density of and an electron temperature of 2 eV. In addition, the gas temperature of 120 °C has been spectroscopically measured inside the discharge. These plasma parameters indicate that the APPJ shows promise for various materials applications as it can produce substantial amounts of reactive species and avoid thermal damages, while having the advantage of atmospheric pressure operation.
Investigation of the gas pressure influence on patterned platinum etching characteristics using a high-density plasma89(2001); http://dx.doi.org/10.1063/1.1330554View Description Hide Description
A high-density surface-wave magnetized argon plasma operated in the very low pressure regime together with a rf biased system is used to study the pure physical etchingcharacteristics of platinumthin films. It is shown that, for a given dc self-bias voltage, the platinumetch rate strongly decreases as the operating pressure increases, which results from a decrease of the ion density at the sheath edge and from enhanced redeposition. It is found that using a high-density plasma in the very low pressure regime yields high etch rates with a good selectivity over resist. Fence-free features can also be achieved at bias voltages that, in contrast with reactive ion etching reactors, are only slightly above the platinum sputtering threshold.
89(2001); http://dx.doi.org/10.1063/1.1285843View Description Hide Description
The effect of particulate size on the spatial distribution of dust in a plasma environment is investigated through the simulation of a dust transportmodel coupled with plasma and neutral models. The dust transportmodel takes into account all important factors affecting dust behavior (gravitational, electrostatic, ion drag, neutral drag and Brownian forces). A Lagrangian approach is employed for the simulation of the dust transportmodel, tracking the individual trajectory of each particulate by taking a force balance on the particulate. Trap locations, for dust particles of sizes ranging from a few nm to a few μm, are identified in an electropositive plasma. The simulation results show that dust particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a “dome” shape around the center of the plasma reactor and are also trapped in a “ring” near the radial sheath boundaries, while larger particles accumulate only in the “ring.” These simulation results are qualitatively in good agreement with experimental observation.