Selected-area Deposition of Diamond Films on Silicon Nitride-coated Silicon Substrates Using Negatively Biased Microwave Plasma Enhanced Chemical Vapor Deposition Technique

Abstract

Selected-area deposition (SAD) of diamond films has been successfully grown on silicon substrates, using silicon-rich nitride (SiN) precoatings and a negatively biased microwave plasma enhanced chemical vapor deposition technique. However, diamond growth is limited on stoichiometric nitride ( Si3N4) precoatings, which are ascribed to the insulation of these layers. The application of a negative bias voltage is thus blocked. Lowering the total pressure in the CH4/H2 mixture from 75 Torr to 60 Torr significantly suppresses the nucleation of diamonds on the Si-substrate, without modifying it on the SiN-substrate, so that a high selectivity (>200) SAD diamond film is obtained. Optical emission spectroscopy (OES) indicates that the large etching rate on the Si-surface, due to the reduction in the carbonaceous-to-hydrogen ratio, is the main factor of nucleation suppression. Scanning electron microscopy (SEM) and Raman spectroscopy indicate that the SAD and the quality of diamonds is optimized under deposition conditions such as 60 Torr total pressure, 2500 W microwave power, CH4-to-H2=15:300 sccm and 120 VDC bias.