Electrical properties of Ge metal-oxide-semiconductor capacitors with La2O3 gate dielectric annealed in different ambient

Ge metal-oxide-semiconductor capacitors with La2O3 as gate dielectric are fabricated by e-beam evaporation of La2O3 followed by post-deposition annealing in different gases (NH3, N-2, NO, N2O and O-2). Experimental results indicate that the NH3, NO, N2O and O-2 anneals give higher interface-state and oxide-charge densities, and thus larger gate leakage current, with the highest for the O-2 anneal due to the growth of an unstable GeOx interlayer. On the other hand, the NH3 annealing improves the k value of the dielectric, while the annealings in O-2-containing ambients (NO, N2O and O-2) lead to the formation of a low-k GeOx interlayer, thus decreasing the equivalent k value. Compared with the above four samples, the sample annealed in N-2 exhibits not only larger k value (18.3) and smaller capacitance equivalent thickness (2 14 nm), but also lower leakage current density (similar to 10(-3) Acm(-2) at V-g = 1 V) and smaller interface-state density (4 5 x 10(11) eV(-1) cm(-2)). (C) 2010 Elsevier B.V. All rights reserved.