AN INVESTIGATION OF ELECTROMAGNETIC-FIELD PATTERNS DURING MICROWAVE PLASMA DIAMOND THIN-FILM DEPOSITION

The electromagnetic field patterns and intensities of a microwave-sustained, diamond thin film deposition discharge were measured in a microwave plasma disk reactor (MPDR). The MPDR is a cylindrical, symmetrical cavity applicator which can be excited in single electromagnetic modes and utilizes internal matching and thus lends itself to experimental electromagnetic field diagnosis. The measured electric field intensities indicate that the plasma-loaded TM011 mode provides optimum discharge excitation. During the thin film deposition conditions of 30–100 Torr and 100–300 sccm with mixtures of H2/CH4, the electric field intensities in the applicator are 100–200 V/cm and the tangential component of the electric field is the major electric field exciting the discharge. Measured discharge-loaded cavity quality factors are 70–100 and microwave coupling efficiencies into the discharge are in excess of 98%; i.e., the transfer of microwave energy to the discharge is a very efficient process. Using estimated discharge electron neutral-collision frequencies and electron and ion densities, calculations indicate that discharge electromagnetic skin depths vary from 2–5 cm during thin film deposition. It is believed that maximum discharge size is limited by this electric field depth of penetration. © 1990, American Vacuum Society. All rights reserved.