Comparison of modifications induced by ArF excimer laser irradiation on silicon nitride films deposited by different LCVD methods

Abstract Hydrogenated amorphous silicon nitride (a:SiN:H) films produced by CO 2 and ArF laser-induced CVD in parallel configuration using silane/ammonia or disilane/ammonia gas mixtures were subjected to room-temperature multiple pulse ArF excimer laser irradiations in an inert gas atmosphere. Modifications in their chemical composition, refractive index, and surface morphology were systematically followed up through Fourier-transform infra-red spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), single-wavelength ellipsometry and atomic force microscopy (AFM), respectively. The observed film modifications involving large reductions in hydrogen (Si-H and N-H) with the first few shots and accompanied by a progressive incorporation of oxygen (Si-O and Si-OH) and a reduction of Si-N bonds are attributed to UV-induced photochemistry where the atmospheric water incorporated in the films between successive irradiations plays an important role. For the same number of irradiation shots, the CO 2 laser-deposited film using silane underwent the greatest extent of compositional and morphological modifications, followed by the ArF-deposited film using silane, and the least modified film was the ArF-deposited film using disilane. Comparison among the different films indicated that the extent of bonded hydrogen in the films and their surface morphology influence their oxidation resistance.