This work reports on the optimization of Yo.9 Er0.1 Al3(BO3)4 thin films for integrated optics. The films were deposited on silica and silicon substrates using the spin-coating technique involving solutions previously prepared by the polymeric precursor method. These deposits, 400-800 nm thick, were prepared by a 5-10 multi-layer process and heat treatments at different temperatures from glass transition to crystallization temperature, using heating rates of 2 or 5 degrees C/min. The structural characterizations were performed using grazing incidence X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR). Water and/or hydroxyl contents were also evaluated from FT-IR spectra. Microstructural evolution in term of annealing temperatures was analyzed by high resolution scanning electronic microscopy and atomic force microscopy. Optical transmission spectra were used to determine the refractive index and thickness through the envelope method of the films. Finally, the film guiding and optical properties were studied by m-line spectroscopy. The best film showed a good waveguiding with high light-coupling efficiency close to the theoretical limit.