Numerical simulation and realisation
of NOVEL microwave plasma reactors for diamond cvd

C. Wild, E. Pleuler, W. Müller-Sebert, P. Koidl

Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg, Germany
E-mail: wild@iaf.fhg.de, Homepage: www.cvd-diamond.com

Abstract

The development of efficient microwave plasma reactors for diamond CVD is an important issue for the production of large area, high quality diamond disks. In this context numerical simulations using FEM algorithms that allow a self-consistent determination of the electric field and plasma density distribution in microwave plasma reactors have found considerable interest. The talk will describe the numerical concepts applied and the validation of the simulation results.

Two types of microwave plasma reactors have been realized. One exhibits an ellipsoidal cavity with two focal points. By coupling microwave energy into one focal point, high electric fields can be generated in the second one. This in turn can be exploited for the excitation of intense plasmas. This ellipsoidal reactor is now used as a "workhorse" for the routine production of diamond disks.

As an alternative a second reactor concept has been studied. In this reactor the microwave enters the plasma chamber through a ring-shaped circumferential window. The microwave is guided to the window by radially expanding a coaxial waveguide. Simulation results, measurements performed with a miniature microwave sensor and preliminary performance tests will be presented for this CAP-reactor (circumferential antenna plasma reactor).

Furthermore, the properties of CVD diamond disks and their applications in optics (radiation windows and lenses), thermal management (heat spreaders) and mechanics (wear resistant components) will be described.

Keywords: microwave plasma reactor, numerical simulation, diamond disks