Apparatus for controlling plasma size and position in plasma-activated chemical vapor deposition processes comprising rotating dielectric

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Those of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting.
While the present disclosure utilizes formation of CVD diamond material as an illustrative example, those of ordinary skill in the art will appreciate the applicability of the principles of the present invention to CVD deposition techniques for other materials as well.
Other embodiments of the invention and applications therefor will readily suggest themselves to such skilled persons.
According to a first aspect of the present invention, a small plasma can be made to move back and forth over a controlled area in a CVD rector at a rate which is rapid compared to the decay time of the excited species it produces.
Such a moving plasma is for all chemical purposes equivalent to a large, stationary plasma.
Plasma motion can be achieved by modulating the phase of incident and/or reflected waves which comprise the standing wave pattern which determines plasma location.
Referring first to FIGS.
1a-1c, a presently preferred power-efficient means for inducing plasma motion according to the present invention employs appropriate phase modulation of both incident and reflected waves.
FIGS.
1a-1c show the relationships between incident and reflected waves in a typical microwave CVD diamond reactor.
FIG.
1a shows the condition in chamber 10 in which an incident wave 12 introduced into chamber 10 via waveguide 14 and a reflected wave 16 from sliding short or stub 18 moveable within waveguide 20 are in phase and intersect in the middle of the chamber 10.
The heavier trace 22 in FIG.
1a represents the resultant composite wave from the summing of waves 12 and 16.
The cross-hatched oval 24 indicates the location of a plasma region in chamber 10 under the conditions of FIG.
1a.
This is the normal condition encountered in a microwave CVD plasma reactor operated in the so called cavity mode.
FIG.
1b shows the condition in which a phase shift has been imposed on the reflected wave 16 by moving the sliding short or stub 18 further into waveguide 20