Mechanical properties of boron nitride thin films obtained by RF-PECVD at low temperatures

This work describes the thermomechanical and structural modifications induced by the deposition conditions, in RF-PECVD-produced boron nitride thin films. The samples were prepared at low temperatures (< 400<degrees>C) using B2H6, N-2 and H-2 as gaseous precursors. The B2H6/N-2 flow ratio, the B2H6 flow, the N-2 flow, the substrate temperature, the r.f. power and the H-2 dilution were varied. The structure and composition of the films as well as the thermomechanical properties, such as stress and hardness, were studied and correlated with each other and with the deposition parameters. It was found that the films present a mixture of hexagonal and amorphous phases and, under certain conditions, evidences of cubic phase. The fraction of these phases as well as the crystallite size, deduced by Raman spectroscopy, depend strongly on the B2H6 flow, the B2H6/N-2 flow ratio and on the H-2 dilution. A boron/nitrogen ratio, close to stoichiometry was obtained for all the studied samples. (C) 2000 Elsevier Science S.A. Ail rights reserved.