Varied SiNx films have been deposited by low pressure chemical vapor deposition from silane SiH4 and ammonia NH3 and the influences of the deposition parameters (temperature, total pressure and NH3/SiH4 gaseous ratio) on the film deposition rate, refractive index (assessed at a 830 nm wavelength), stoichiometry and thermomechanical stress are investigated and correlated. Low stress (≈600 MPa) Si3N4 films are obtained for the highest deposition temperature and the lowest total pressure but the gaseous ratio is shown to be the dominant parameter. According to the SiNx stoichiometry, silicon-rich silicon nitride and nitrogen-doped silicon (called NIDOS) depositions are obtained and compressive to tensile stresses are reported. A maximum in compressive stress is put into evidence for N/Si ratio roughly equal to 0.7 and is related to the cumulated effects of silicon nitridation and crystallization, characterizing the transition between nitrogen-doped silicon and silicon-rich silicon nitride. Finally, by considering stress, deposition rate, nonuniformity along the load and resistance to alkaline solutions, optimal (silicon-rich) silicon nitride deposition conditions are proposed for microelectromechanical applications.

Detailed investigation of the surface mechanisms and their interplay with transport phenomena in alumina atomic layer deposition from TMA and water. (2019) Chemical Engineering Science. 195. 399-412.

During the first stages of Atomic Layer Deposition (ALD) of Al2O3 on silicon (Si), the substrate nature affects the surface chemistry, leading to an initial island growth mode. Furthermore, an interfacial zone develops between the Si surface and the dielectric, thus damaging the physical properties of the deposited structure. In this work, these two main shortcomings are investigated for the ALD of Al2O3 films on Si from TMA and H2O. The film and the interfacial zone are characterized by a complete range of techniques, including XRR, TEM, XPS, EDX and ToF-SIMS. In parallel, a computational model is developed to study the initial nucleation and growth steps of the film. An induction period is experimentally evidenced and numerically reproduced, together with the island growth and coalescence phenomena. The chemical composition of the (Al, O, Si) interfacial layer is precisely analyzed to get insight in the mechanisms of its formation. We show that Si oxidation occurs during the island growth, catalyzed by the presence of Al, while it is also fed by species interdiffusion through the ALD film.