In situ characterization of boron nitride layer growth by polarized FTIR reflection spectroscopy

Layers of almost pure cubic boron nitride (c-BN) have been deposited in a h ollow cathode are evaporation device on silicon and titanium nitride substr ates. The layer growth is analyzed by in situ polarized infrared reflection absorption spectroscopy (IRRAS). The spectra are sensitive to determine th e phase of the growing film due to the different phonon absorption frequenc ies of hexagonal BN (h-BN) and c-BN. The optical set-up can be used either as infrared spectroscopic ellipsometer (IRSE) in a rotating analyzer config uration or as IRRAS with variable state of polarization. For a quantitative analysis the spectra have been simulated with a three-layer model consisti ng of the substrate, the h-BN interface layer and the c-BN layer. To calcul ate the dispersion relation of the BN layers we used a Lorentz oscillator m odel. The oscillator frequency is correlated to the stress in the c-BN film s, which is one of the delimiting factor for the deposition of thick films. Evaluating the oscillator frequency by a simulation procedure it is possib le to determine the stress of the c-BN films in situ as a function of depos ition conditions. The data received by IRSE and IRRAS are compared and the error sources are discussed. (C) 2000 Elsevier Science S.A. All rights rese rved.