Ultra‐thin nanocrystalline diamond films (<100 nm) with high electrical resistivity

Thick diamond films are known to exhibit remarkably high electrical resistivity and thermal conductivity. However, on thin films, difficulties are often observed to achieve such performances. In this study, the synthesis of ultra‐thin diamond films was optimized towards the possibility to maintain high dielectric performances on layers compatible with today requirements for Silicon‐On‐Diamond technology, and namely aiming at films with thicknesses equal or below 150 nm. The nucleation of diamond nanocrystals is crucial to obtain films with thickness lower than 100 nm. A Bias Enhanced Nucleation step (BEN) was improved to achieve nucleation densities above 10¹¹ cm^–2 although the process was also tuned to limit the size of the nanocrystals during this step. The control of the carbonization of the silicon substrate is also essential to reach such a density with a high reproducibility. The BEN is followed by a growth step with optimized conditions. The films were characterized by SEM and Spectroscopic Ellipsometry. Electrical conductivity measurements were conducted on thin diamond films and values obtained on layers below 100 nm were as high as 5 × 10¹³ Ω cm; a value significantly higher than the state of the art for such thin films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)