Atomic Layer Deposition of Hafnium Oxide on Ge and GaAs Substrates: Precursors and Surface Preparation

Abstract

To increase complementary metal oxide semiconductor (CMOS) device performance, new materials are introduced in the gate stack (high-k dielectrics and metal gates) and the transistor channel (Ge, III-V materials). In this work we study the atomic layer deposition (ALD) of hafnium oxide on Ge and GaAs substrates. Passivation layers are required to achieve a sufficiently low interface state density, but these might also influence the growth behavior and dielectric quality. Therefore, we investigate the effect of surface preparation, for example, native oxide, wet clean, thermal oxidation, and S-passivation, for the HfCl(4)/H(2)O and tetrakis diethylamino hafnium=((C(2)H(5))(2)N)(4)Hf (TDEAH)/H(2)O processes. The growth of HfO(2) from initial submonolayer coverage to continuous HfO(2) film is studied by means of Rutherford backscattering, static time-of-flight secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy. HfCl(4)/H(2)O ALD depends on the surface preparation. The growth is enhanced on oxide surfaces (thermally grown GeO(2), HF-cleaned Ge, and GaO(x)-AsO(y)) and inhibited on oxide-free substrates (HBr-cleaned Ge). The initial island growth regime is least pronounced on germanium oxide. In contrast, TDEAH/H(2)O ALD is independent of the surface preparation. The growth is inhibited in the first similar to 20 cycles on native oxide and S-passivated GaAs [(NH(4))(2)S treatment], but the initial island growth regime is quickly followed by the two-dimensional growth regime. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2979144] All rights reserved.