Large area microwave plasma CVD of diamond using composite right/left-handed materials

Abstract

Diamond growth at low temperatures (<400 degrees C) and over large areas is attractive for materials, which are sensitive to high temperatures and require good electronic, chemical or surface tribological properties. Resonantcavity microwave plasma enhanced (MWPE) chemical vapor deposition (CVD) is a standard method for growing diamonds, however, with limited deposition area. An alternative method for CVD of diamond over large area and at low temperature is to use a surface wave plasma (SWP). In this work we introduce a novel method to excite SWP using composite right/left-handed (CRLH) materials and demonstrate growth of nanocrystalline diamond (NCD) on 4-inch Si wafers. The method uses a set of slotted CRLH waveguides coupled to a resonant launcher, which is connected to a deposition chamber. Each CRLH waveguide supports infinite wavelength propagation and consists of a chain of periodically cascaded unit cells. The SWP is excited by a set of slots placed to interrupt large area surface current on the resonant launcher. This configuration yields a uniform gas discharge distribution. We achieve 80 nm/h growth rate for NCD films with a low surface roughness (5-10 nm) at 395 degrees C and 0.5 mbar pressure using a H2/CH4/CO2 gas mixture.