Two-dimensional model of a large area, inductively coupled, rectangular plasma source for chemical vapor deposition
A novel design for an inductively coupled, rectangular plasma source is described. The design encompasses several key issues of large area thin film growth by chemical vapor deposition: structural integrity, electrostatic screening, substrate temperature control and maximal growth surface. A test reactor has been utilized to grow diamond films over ~1800 cm2 at 13 MHz and ~1 torr pressure with 45 kW coupled power. The design is readily scalable to larger areas. To analyze the axial plasma uniformity, a two-dimensional (2-D) simulation model is presented. The electromagnetic coupling, nonequilibrium plasma chemistry and multispecies diffusion are self-consistently treated. In this 2-D approach, the slotted Faraday screen behaves as a diamagnetic medium in transmitting the magnetic field. Results are compared with experimental data for the hydrogen plasma extent, electron and gas temperatures. Neutral gas thermal conduction and hydrogen recombination dominate the energy deposition to the wall and in turn govern the plasma length. A tradeoff between quality and growth area is predicted for the reactor as the pressure is decreased.