It was reported that a 5nm thick Al2O3 film grown on Si(100) directly by sputtering exhibited strong (110) texture, accompanied by a shrunk lattice structure (Δd/d ~-2.36%). The disordered nature of the film was confirmed by cross-sectional high-resolution transmission electron microscopy, implying the loosened microstructure responsible for enhanced interdiffusion. The O-deficient Al2+δO3-δ(δ>0) interdiffusion region with complex interfacial chemical valences was formed between the Al2O3 film and Si substrate, reducing the insulator properties. Using depth profiling in situ X-ray photo-emission spectroscopy, the non-stoichiometry deviation of the Al/O ratio at the interdiffusion region was quantitatively revealed. A nominal thickness of 5nm was required in order to obtain an actual barrier thickness of approximately 1nm.

Shrunk Lattice Structure and Interdiffusion Characteristics of 5nm Thick Al2O3 Ultrathin Films Sputtered on Silicon. J.M.Li: Nanotechnology, 2008, 19[3], 035604 (5pp)