Preparation and Properties of Amorphous Boron Nitride Films by Molecular Flow Chemical Vapor Deposition

A new chemical vapor deposit ion method of thin film in molecular flow region (MF-CVD) is proposed, and is ap-plied to the preparat ion of boron hitr ide films using ammonia and decaborane reaction gases. It is found that the com-posit ion of the films can be closely control led by regulating the pressure of source gases and stoichiometric boron ni-tride films deposited at NH3/B10H,4 => 20 at the substrate temperature of 850 ~ From the chemical shift of boron K~2 peak in the x-ray f luorescence spectra, the BNx films having the composit ion x < 0.75 are mixture of boron and boron nitride. X-ray diffraction study indicates that the films are amorphous. The optical properties of the boron itr ide films are also clarified. The energy of the direct al lowed transition is estimated to be 5.90 eV. Boron nitr ide has properties such as being electrically insulating, chemical ly inert, thermal ly stable, resistant o corrosion, and having desirable mechanical properties, and is considered to be one of wide bandgap semiconduc-tors. Potential applications of boron nitride films have been proposed such as high temperature dielectrics (1), heat-dissipation coatings (2), passivation layers (3), diffu