ABSTRACTWe present an in situ study of the growth of boron nitride thin films by real time ellipsometry. Films were produced in a PECVD reactor by rf glow discharge decomposition of ammonia (pure) and diborane (1% in hydrogen), on Ni-Cr coated c-Si substrates placed either on the powered electrode or on the grounded electrode of the reactor. A fast phase-modulated ellipsometer performed the real time monitoring of the growth processes at 350 nm. The ellipsometric angle trayectories were obtained through an autocalibrated method, especially suitable for the in situ optical analysis of transparent thin films. We applied several thin film growth optical models (homogeneous, two-layer, surface roughness) to analyze parameters of the films such as refractive index, extinction coefficient, roughness and deposition rate. In all the cases studied, the two-layer model fits well with the ellipsometric measurements, but a more sofisticated model considering a variable refractive index could better describe these films.
