We experimentally find that there are hot and cold electron components present in a sputtering magnetron plasma. The density of the hot component is greatest in the magnetic trap and decreases with the distance from the cathode. The cold electron density is negligible inside the trap and is approximately constant outside. The largest cold electron density is nearly as great as the hot electron density inside the magnetic trap.

A particle model of energetic electron transport in sputtering magnetron discharges is presented. The model assumes time-independent magnetic and electric fields and supposes that scattering by neutral atoms is the dominant transport mechanism. Without scattering, we find that some orbits are confined indefinitely. Using the differential cross sections for elastic, excitation, and ionization collisions in argon, we perform a Monte Carlo simulation of the electrons emitted by ion bombardment of a planar magnetron cathode to predict the spatial distribution of ionization. We find good agreement with experimental measurements of the radial profile of ion flux to the cathode and of the axial profile of optical emission.

Using laser-induced fluorescence, the ion velocity and density inside a dc plasma sheath have been measured. A polished planar electrode, biased at −100 V, was aligned so that a laser beam struck it at normal incidence. Using this arrangement, the ion velocity component perpendicular to the electrode surface was measured. By detecting the fluorescence while scanning the laser frequency, a line shape was recorded that had two peaks, due to the Doppler shift from the incident and reflected beams. The separation of the peaks yielded an absolutely calibrated measure of the ion drift velocity, while the height of the peaks gave the ion density. As expected, in the sheath the measured ion density was lower and the velocity was higher than in this plasma. Using these measurements, it was confirmed that the ion flux is conserved in a sheath. The spatial profiles of ion velocity and density in the sheath were used to test a time-independent two-fluid theory, and good agreement was found. The data were also compared to Child’s law, which showed good agreement near the electrode but predicted the density poorly, as expected, near the plasma–sheath boundary.

One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for

The electron distribution function g(v z ) in a cylindrically symmetric, planar, sputtering magnetron has been characterized using a one-sided, planar Langmuir probe. Measurements were made above the magnetic trap at six radial locations in the direction normal to the cathode. The distribution function is found to be non-Maxwellian, with a shape that depends sensitively on radial position. Near the symmetry axis, g(v z ) is anisotropic and exhibits a strong electron drift from the cathode to the anode. Off axis, g(v z ) is nearly symmetric and has two components: a dense, cold Maxwellian component, and a tenuous, energetic shell component.

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A much greater number of useful precursors for plasma-enhanced chemical vapor deposition (PECVD) can be dispersed in high vapor pressure solvents than can be put into the vapor phase directly. In order to enable the use of such precursors, the authors investigated a method by which one can directly inject these liquids as microdroplets into low pressure PECVD environments. The solvent evaporates first leaving behind the desired precursor in the gas/plasma. The plasma dissociates the vapor and causes the deposition of a composite film (from precursor, solvent, and plasma gas). The authors made preliminary tests using Fe nanoparticles in hexane and were able to incorporate over 4% Fe in the resulting thin films. In addition, the authors simulated the process. The time required for a droplet to fully evaporate is a function of the background pressure, initial liquid temperature, droplet-vapor interactions, and initial droplet size. A typical evaporation time for a 50μm diameter droplet of hexane is ∼3s without plasma at 100mTorr. The presence of plasma can decrease the evaporation time by more than an order of magnitude. In addition, the model predicts that the temperature of the injected droplet first decreases by evaporative cooling (to ∼180K for hexane); however, once the solvent has fully evaporated/sublimated, the plasma heats any remaining solute. As a result the solute temperature can first fall to 180K, then rise to nearly 750K in less than 1s.

The first direct measurement of a collisional Bohm presheath from plasma potential measurements is given. By measuring the presheath thickness in front of a grounded wafer stage, a determination of the collision mean free path for ions in an electron cyclotron resonance etching tool has been made. Presheaths were measured in N, and CF, plasma using an emissive probe. The presheath thickness in N, was found to be linearly dependent on the mean free path. Measurements of CF, plasmas, for which the collision cross sections are unknown, have shown results similar to those found for nitrogen. This result has enabled an extrapolation to be made of the effective cross section for collisions in plasmas created from CF,.