INFRARED KINETIC-STUDY OF ULTRATHIN SIC BUFFER LAYERS GROWN ON SI(100) BY REACTIVE CHEMICAL-VAPOR-DEPOSITION

A kinetic study was carried out on the growth of an SiC buffer layer o n Si(100) by reactive chemical vapour deposition. Experiments were per formed at temperatures in the range 1150-1300 degrees C for 1 to 45 mi n using C3H8 and H-2 as gas reactants. Infrared transmittance spectrom etry was used for accurate film thickness determination (down to 1.2 n m). The growth profiles as a function of time show a four-step mechani sm involving the rapid formation of an SiC ''thermal layer'' by coales cence of SiC islands. The thickness increases by Si out-diffusion thro ugh this layer until a critical thickness, controlled by the temperatu re and Si etching, is reached. Only the initial values of the diffusio n profiles can be fitted by Fick's second law. The hypothesis of silic on etching by H-2 is confirmed by thermodynamic calculations. The etch ing activation energy is E(e) = 4.4 eV. The temperature dependence of the resulting diffusion coefficients gives an apparent diffusion activ ation energy of E(d) = 4.5 eV. The close agreement between these two a ctivation energies illustrates the competition between the two mechani sms deduced from the growth profiles.