MODEL FOR A LARGE-AREA MULTIFREQUENCY MULTIPLANAR COIL INDUCTIVELY-COUPLED PLASMA SOURCE

A model for a large area multifrequency multiplanar coil inductively c oupled plasma (ICP) source is presented. Typical ICP sources employ a single coil that is engineered to provide optimum plasma uniformity fo r large area processing. Pulsed sources have also been developed to im prove etch selectivity via increased radical generation and lower net ion densities. The source described here potentially achieves a combin ed pulsed mode and the capability of moving the plasma source from inn er to outer radii in a controlled fashion (raster mode) for very large area applications. The model consists of a coupled steady-state two-d imensional ambipolar diffusion model, an electromagnetics model, and a lumped parameter circuit model. While stable operation is possible, t he model shows that the scheme is found to be very sensitive to coil-t o-coil coupling and to the ordering of the phases and frequencies of t he coils. Examples of stable operation of a three coil set device are presented: Results suggest that frequency control may be an attractive control variable for real time control of large area plasma processes . (C) 1996 American Vacuum Society.