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    Plasma Science Monday Sessions
       Session PS1+MM-MoM

Paper PS1+MM-MoM7
Potential and Current Profiles of Nitrogen Gas DC Microplasmas

Monday, October 29, 2001, 11:40 am, Room 103

Session: Science & Technology of Microplasmas and MEMS Processing
Presenter: C.G. Wilson, University of Wisconsin-Madison
Authors: C.G. Wilson, University of Wisconsin-Madison
Y.B. Gianchandani, University of Wisconsin-Madison
A.E. Wendt, University of Wisconsin-Madison
Correspondent: Click to Email
We have recently reported on@footnote 1@ DC microplasmas which have been generated between patterned thin-film metal electrodes on the surface of a wafer. Typical operating pressure and power density are in the range of 1-20 Torr and 1-10 W/cm@super 2@, respectively. The plasma extent can be varied from <100 µm to >1 cm by variations in the electrode area, operating pressure and power. Silicon etch rates of 4-17 µm/min have been achieved. This technology allows multiple independent etching microplasmas to be operated on a single silicon wafer, enabling parallel or consecutive processing. Applications for this include trimming of electronic and micromechanical components, ranging from resistors to resonant gyroscopes. In this paper we will report on characteristics of microplasmas generated by co-planar in-situ electrodes. Breakdown voltage has been found to differ from the Paschen curve, being more uniform over a wider range of pressures. Contour plots of the floating potential of microplasmas have been measured, and the bulk of the voltage drop in the plasma column has been found to be proximate to the cathode. The floating potential is non-uniform at equal heights over the cathode and is lowest close to the center of the electrode. The height of the plasma column is found to scale with operating pressure, ranging in height from 3000-900 µm as pressure changes from 1.2-6 Torr. The internal voltage drop in the plasma column is considerable, and varies with the power density and pressure. At lower pressures, the current is found to be denser at the outer edges of the electrodes, and at higher pressures the current moves to the inner edges, becoming more uniform as the power density increases. We explore the effects of these results on silicon etching performance. @FootnoteText@ @footnote 1@ C.G. Wilson, Y.B. Gianchandani, "Silicon Micromachining Using In Situ DC Microplasmas," Journal of Microelectricalmechanical Systems, Mar. 2001, pp. 50-54.