Ultrafine patterning of nanocrystalline diamond films grown by microwave plasma-assisted chemical vapor deposition

The growth of nanocrystalline diamond films having an appropriate surface smoothness for nanoscaled ultrafine patterning was investigated. The surface smoothness of polycrystalline diamond films was controlled by introducing nitrogen (N-2) gas at concentrations ranging from 0 to 1.0% into the gas mixtures of methane (CH4) and hydrogen (H-2) on microwave plasma-assisted chemical vapor deposition (MPCVD). The added 1.0% N-2 with 10% CH4 in the gas phase yielded the desired diamond film with the smoothest surface among the conditions. An N-doped nanocrystalline diamond film was fabricated by nanoscaled ultrafine patterning by e-beam lithography followed by reactive ion etching (RIE). As a mask material in RIE, we found that a chemical vapor-deposited amorphous silicon nitride film is appropriate. A mixture consisting of oxygen and a small amount of tetrafluoro carbon was used as the etching gas. We succeeded in achieving a minimum line width of 100nm in the N-doped nanocrystalline diamond film with our fabrication process.