Layers of almost pure cubic boron nitride (c-BN) have been deposited in a hollow cathode are evaporation device on silicon and titanium nitride substrates. The layer growth is analyzed by in situ polarized infrared reflection absorption spectroscopy (IRRAS). The spectra are sensitive to determine the phase of the growing film due to the different phonon absorption frequencies 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 configuration or as IRRAS with variable state of polarization. For a quantitative analysis the spectra have been simulated with a three-layer model consisting of the substrate, the h-BN interface layer and the c-BN layer. To calculate the dispersion relation of the BN layers we used a Lorentz oscillator model. The oscillator frequency is correlated to the stress in the c-BN films, which is one of the delimiting factor for the deposition of thick films. Evaluating the oscillator frequency by a simulation procedure it is possible to determine the stress of the c-BN films in situ as a function of deposition conditions. The data received by IRSE and IRRAS are compared and the error sources are discussed.