Electrical properties of Ge metal-oxide-semiconductor capacitors with La 2O 3 gate dielectric annealed in different ambient

Abstract

Ge metal-oxide-semiconductor capacitors with La 2O 3 as gate dielectric are fabricated by e-beam evaporation of La 2O 3 followed by post-deposition annealing in different gases (NH 3, N 2, NO, N 2O and O 2). Experimental results indicate that the NH 3, NO, N 2O 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 GeO x interlayer. On the other hand, the NH 3 annealing improves the k value of the dielectric, while the annealings in O 2-containing ambients (NO, N 2O and O 2) lead to the formation of a low-k GeO x 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 AR (∼ 10 -3 Acm - 2 at V g = 1 V) and smaller interface-state density AR (4.5 × 10 11 eV - 1 cm - 2). © 2010 Elsevier B.V.