Lanthanum aluminate by atomic layer deposition and molecular beam epitaxy

A comparison of physical and electrical characteristics of lanthanum aluminate (LAO) dielectrics formed by atomic layer deposition (ALD) and molecular beam epitaxy (MBE) is investigated in this study. Physical characteristics of LAO deposited with these two deposition methods are compared using x-ray photoelectron spectroscopy (XPS), transmission electron rnicroscopy (TEM). and secondary ion mass spectrometry (SIMS). Capacitors with TaN and TaSiN gate electrodes were fabricated to assess electrical properties of these LAO films, ALD LAO was deposited using La[N(SiMe3)(2)](3), Al(CH3)(3) and water at 225-275 degrees C. ALD LAO is stable against Pt and TiN/W metal gates up to 800 degrees C. After annealing at 900 degrees C, interactions between metal gates and dielectrics are observed resulting in nonfunctional devices. MBE LAO film was deposited at room temperature or 200-400 degrees C in two ways: Using single element targets (La, Al) or a compound target. The LAO/TaN stack deposited with single element targets showed significant Si tip diffusion from the substrate to the dielectric and the metal gate electrode. In addition, nitrogen diffusion from the metal gate into the dielectric was detected. The LAO/TaN stack deposited with a compound target showed improved thermal stability. No metal out-diffusion and only verb slight Si out diffusion was detected after a 900 degrees C anneal. LAO capacitors show well-behaved capacitance-voltage and leakage current density-voltage characteristics. These results indicate that the method by which lanthanum aluminate films are deposited strongly influenced their thermal stability. Of all the films examined. the most stable films are deposited by MBE using a compound target. (D 2005 American Vacuum Society.