LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION OF B-N-C-H FILMS FROM TRIETHYLAMINE BORANE COMPLEX

In this study, films consisting of B-N-C-H have been synthesized by lo w pressure chemical vapor deposition using the liquid precursor trieth ylamine borane complex (TEAB) both with and without ammonia. When no N H3 is present, the growth rate was observed to follow an Arrhenius beh avior in the temperature range of 600 to 800 degrees C with an apparen t activation energy of 11 kcal/mol. A linear dependence of growth rate is observed as a function of square root of flow rate for the TEAB ra nge of 20 to 60 seem, indicating that the reaction rate is controlled by the adsorption of borane. The addition of NH3 to TEAB had the effec t of lowering the deposition temperature down to 300 degrees C and inc reasing the apparent activation energy to 22 kcal/mol. Above 650 degre es C, the carbon concentration of the deposits increased significantly , reflecting the breakup of the amine molecule. X-ray diffraction meas urements indicated the films to be in all cases amorphous. Infrared sp ectra of the films showed absorption peaks representing the vibrationa l modes of B-N, B-N-B, B-H, and N-H. The index of refraction varied be tween 1.76 and 2.47, depending on composition of the films. Films depo sited with no NH3 above 700 degrees C were seen to be compressive whil e films below that temperature were tensile. In the range of 350 to 47 5 degrees C, the addition of NH3 to TEAB resulted in films that were m ildly tensile, while below 325 degrees C and above 550 degrees C, the films were found to be compressive. Both the hardness and Young's modu lus of the films decreased with higher temperatures, reflecting the in fluence of the carbon presence.