PLASMA-ASSISTED CHEMICAL-VAPOR-DEPOSITION OF BN COATINGS - EFFECT OF THE EXPERIMENTAL PARAMETERS ON THE STRUCTURE OF THE FILMS

Boron nitride (BN) coatings have been deposited in a hot wall PACVD re actor with a capacitive coupling at 13.56 MHz, from BCl3/N2H2/Ar mixtu res. The effect of ion bombardment and the hydrogen content on the nat ure of the BN phases (determined by Fourier transformed infra-red spec troscopy) is highlighted. Gas phase characterisation is performed by o ptical emission spectroscopy (OES), mass spectrometry (MS) and electri cal measurements. The coatings properties are correlated to the plasma characteristics. It is confirmed that well defined ion bombardment co nditions are required for c-BN formation. The hydrogen partial pressur e in the gas phase plays another determining role on c-BN formation by its effect on the concentration of reactive species in the plasma and thus on the deposition rate. Hence, in addition to the ionic selectiv e etching of the h-BN sites over the cubic sites commonly reported, a chemical effect (leading to preferential etching or reaction inhibitio n) due to the presence of the chlorine and atomic hydrogen species at the surface might occur.