Novel high frequency pulsed MW-linear antenna plasma-chemistry: Routes towards large area, low pressure nanodiamond growth

Abstract

Current experimental microwave plasma enhanced chemical vapour deposition (MW PECVD) concepts for diamond thin films do not allow scaling up towards large areas, which is essential for microelectronic industries. Also, current growth temperatures are rather high and not compatible with processing technologies. In the current work we demonstrate a breakthrough concept using a high frequency (HF) pulsed MW-linear antenna plasma configuration, allowing a scalable concept. By using HF pulses non-linear MW absorption conditions are reached, allowing a reduction of input power to 4 W/cm(2) compared with typically 100-200 W/cm(2) for resonance cavity applicators. Despite the factor of 50 power reduction, the growth rate obtained at 450 degrees C is comparable to or higher than that of resonance cavity systems. Our concept is a significant improvement as compared to [1,3] previous methods of nanodiamond growth. The resulting diamond films show columnar growth, i.e. resembling classical nano-crystalline diamond (NCD) films [3], with high crystallinity compatible with silicon on diamond chip technology. We present data from plasma diagnostics, showing HE pulsed data from optical emission spectroscopy (OES) for the CH4-CO2-H-2 gas chemistry and discuss the basic properties of the layers prepared. In comparison to the work 11 we have succeeded in suppression of re-nucleation during the growth and prepared high quality NCD films with 3-7% sp(2) carbon, depending on the growth conditions used, based on Raman measurements for layers as thin as 40 nm. (C) 2011 Elsevier B.V. All rights reserved.