PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION OF BORON-NITRIDE THIN-FILMSFROM B2H6-H-2-NH3 AND B2H6-N-2 GAS-MIXTURES

Highly transparent and stoichiometric boron nitride (BN) films were de posited an both electrodes (anode and cathode) of a radio-frequency pa rallel-plate plasma reactor by the glow discharge decomposition of two gas mixtures: B2H6-H-2-NH3 and B2H6-N-2. The chemical, optical, and s tructural properties of the films, as well as their stability under lo ng exposition to humid atmosphere, were analyzed by x-ray photoelectro n, infrared, and Raman spectroscopies; scanning and transmission elect ron microscopies; and optical transmittance spectrophotometry. It was found that the BN films grown on the anode using the B2H6-H-2-NH3 mixt ure were smooth, dense, adhered well to substrates, and had a textured hexagonal structure with the basal planes perpendicular to the film s urface. These films were chemically stable to moisture, even after an exposition period of two years. In contrast, the films grown on the an ode from the B2H6-N-2 mixture showed tensile stress failure and were v ery unstable in the presence of moisture. However, the films grown on the cathode from B2H6-H-2-NH3 gases suffered from compressive stress f ailure on exposure to air; whereas with B2H6-N-2 gases, adherent and s table cathodic BN films were obtained with the same crystallographic t exture as anodic films prepared from the B2H6-H-2-NH3 mixture. These r esults are discussed in terms of the origin of film stress, the effect s of ion bombardment on the growing films, and the surface chemical ef fects of hydrogen atoms present in the gas discharge. (C) 1998 America n Vacuum Society.