Synthesis of boron nitride films by microwave plasma chemical vapor deposition in fluorine-containing gases

Boron nitride films were deposited on (001) silicon substrates by rf-or dc-bias-assisted microwave plasma chemical vapor deposition in a He-N₂-BF₃-H₂ gas system. Scanning electron microscopy, X-ray diffraction, and infrared and Raman spectroscopies were performed to characterize the films. The deposited films were composed of cubic boron nitride (cBN) and turbostratic and hexagonal boron nitrides with the cubic phase in the range of 50 to 70%. Raman measurements showed both transverse optical (TO) and longitudinal optical (LO) characteristic peaks of cBN. Although these peaks are very broad, this is believed to be the first reliable report on the appearance of clear Raman signals of cBN deposited by microwave plasma chemical vapor deposition.