LOW-TEMPERATURE PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION BORON-NITRIDE

In this paper we present our results concerning deposition of large ar ea boron nitride films by the conventional plasma enhanced chemical va por deposition (PECVD) technique, in a capacitively coupled reactor, f rom nitrogen (N-2) and diborane (B2H6) gaseous mixtures and at pressur es lower than 1 Torr and temperatures between 200 and 500 degrees C. S eries of samples were grown by changing the RF power, the substrate te mperature and the (N-2/B2H6) flow ratio. The characterization of the s amples was carried out mainly by Fourier transform infrared spectrosco py (FTIR) and thickness measurements. The results have been very promi sing and samples grown in appropriate conditions show clearly the infr ared spectra absorption bands characteristic of hexagonal BN material (h BN), without traces of hydrogen bonding, even at temperatures as lo w as 200 degrees C. The material structure shows a strong dependence o n 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 whil e the h BN phase peaks decreased and shifted in frequency. However, fo r lower RF power values and higher B2H6 flows the in-plane hexagonal v ibration increases and the out-of-plane peak decreases and shifts towa rds 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) 1 997 Elsevier Science S.A.