Low‐temperature deposition of nanocrystalline diamond films on silicon nitride substrates using distributed antenna array PECVD system

Abstract

The growth of nanocrystalline diamond (NCD) films on Si3N4 ceramic substrates at low surface temperature using a distributed antenna array plasma‐enhanced chemical vapor deposition (PECVD) process is investigated. The advantage of the considered deposition process for keeping a low growth temperature is demonstrated through microwave electric field simulation and comparisons with microwave cavity systems. The suitable design of the low‐pressure distributed antenna array reactor thus prevents the ceramic substrate from overheating and consequently from film graphitization. Therefore, for the first time NCD/Si3N4 tribosystems are achieved for deposition temperature in the range 250–400 °C. The nature of the ex situ pretreatment carried out on Si3N4 ceramics in order to favor diamond nucleation, as well as temperature variation in the considered range, do not significantly influence the morphology, topography, composition, and microstructure of the NCD films, the characteristics of which remain very close to those of films deposited on Si substrates under the same conditions. Only the growth rate decreases by a factor of two, down to 15–17 nm h−1, when the deposition temperature diminishes from 400 to 250 °C. This behavior is attributed to an activation energy almost substrate‐independent estimated in the range 3.24–3.57 kcal mol−1 for the considered low‐temperature and low‐pressure NCD deposition process using a H2/CH4/CO2 gas mixture.