AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP28
Antenna Configurations for Large Area rf Inductive Plasma Sources

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: M.M. Patterson, University of Wisconsin, Madison
Authors: M.M. Patterson, University of Wisconsin, Madison
T. Lho, University of Wisconsin, Madison
A.E. Wendt, University of Wisconsin, Madison
N. Hershkowitz, University of Wisconsin, Madison
Correspondent: Click to Email
Industrial demands for uniform, high density, low pressure plasma processing over large areas (roughly 300 cm diameter circular substrates) motivate the study of alternatives to the standard spiral antenna design for inductive plasmas. Scaling of the spiral design suffers from several complications including increased voltage requirements (and therefore increased capacitive coupling). In addition, standing wave current variations along the length of the antenna exacerbate azimuthal nonuniformities along the increased spiral length. A possible solution to these problems is to change the connection between the concentric circular antenna loops from serial (spiral) to parallel. This lowers the net inductance (decreasing voltage requirements) and allows for control over the current in concentric loops by connecting an appropriate lumped inductor between them, enhancing uniformity. We have constructed several circular loops, 10, 20, 30, and 40 cm in diameter for use in a planar inductive plasma source of 64 cm inner diameter. Several types of connections are possible: two loops can be connected either in series or parallel, loops can be driven singularly, and more than two loops can be connected and driven in some combination of serial and parallel connections. Langmuir probe measurements of radial ion saturation current profiles in argon discharges show that good uniformity can be achieved over 30 cm diameter circular areas by choosing the appropriate inductor. Preliminary results also indicate that the ratio of inner and outer loop diameters significantly affects uniformity. We will present results that compare the spatial electron density profile with parallel versus serial connection, loop diameter, and the ratio of inner and outer loop diameters, for both serial and parallel connections.