Low temperature plasma enhanced chemical vapour deposition boron nitride

In this paper we present our results concerning deposition of large area boron nitride films by the conventional plasma enhanced chemical vapor deposition (PECVD) technique, in a capacitively coupled reactor, from nitrogen (N-2) and diborane (B2H6) gaseous mixtures and at pressures lower than 1 Torr and temperatures between 200 and 500 degrees C. Series of samples were grown by changing the RF power, the substrate temperature and the (N-2/B2H6) flow ratio. The characterization of the samples was carried out mainly by Fourier transform infrared spectroscopy (FTIR) and thickness measurements. The results have been very promising and samples grown in appropriate conditions show clearly the infrared spectra absorption bands characteristic of hexagonal BN material (h BN), without traces of hydrogen bonding, even at temperatures as low as 200 degrees C. The material structure shows a strong dependence on the RF power and the diborane flow. For the lower studied B2H6 flows and the higher RF power, the onset of a cubic phase was observed while the h BN phase peaks decreased and shifted in frequency. However, for lower RF power values and higher B2H6 flows the in-plane hexagonal vibration increases and the out-of-plane peak decreases and shifts towards higher frequencies. The temperature did not show a very important effect on the films properties, except for the highest studied value (500 degrees C) for which onset of cubic phase was also observed. (C) 1997 Elsevier Science S.A.